At what point can you say you are flexible enough? I'll agree that daily (or 2-3 weekly) stretching is a fine thing and makes you feel lovely. But I am not one of those rubber women and have never been able to do the splits or get my hands much past my feet regardless of how often I stretch.
These are interesting questions, but not easy ones to answer.
Flexibility requirements are generally task specific – think yoga or gymnastics vs office worker, so it is not easy to say to someone you’re not flexible enough if it is not in context – but someone who is not flexible will not be able to engage in those activities to a high level, without significant risk of soft tissue injury. Outside of a given activity does someone need to be able to touch their toes? Probably not, does this lead to increased injury risk? Probably not, should they attempt to improve flexibility if it is below normal acceptable levels? Probably – if anything it will not do them any harm.
Also worth noting that some people are simply non responders to flexibility training, which you sounds like you might be, no matter how much that train and stretch they don't improve, or they reach a plateau and never move past this point. It's not uncommon and I am not sure anything can be done about this other than trying alternative methods of stretching - particularly heavy load eccentric training as it is proposed to add sarcomeres in series (lengthen muscles).
there is a bit of discussion in this thread from memory
http://www.rotorburn.com/forums/showthread.php?238567-when-is-the-best-time-to-stretch-after-a-ride&highlight=stretching%2C+flexibility
At what point are you functionally flexible? What should we be aiming for? A lack of injury? A lack of stiffness and/or pain?. I'm not 'double jointed' so I don't have absolutely full range of motion, but I think I have reasonably good range of motion. My limbs and joints move smoothly. A good side benefit is that I have very rarely 'sprained' any joint (I think I sprained my ankle once, but it was so long ago I can no longer be sure)
Functionally flexibly would be defined as the ability to engage in activities of daily living, getting dressing, tying shoe laces... these are things oldies do struggle with as they lose flexibility (and strength, coordination). Most younger people will not have this issue and therefore be functionally flexible.
In regards to injury, less flexible people are less likely to have joint (hyperextension) injuries and also flexibility or lack of is not predictive of soft tissue injuries (with the exception of certain movements in specific sports/activities) as most tendon and muscle sprains/strains occur at mid-range in movements. You definitely don’t want to be double jointed, very high chance of reoccurring joint sprains leading to early onset osteoarthritis. While the evidence shows that stretching does not have a dose response, ie. more is not better with a 30-60 second stretch per muscle group being more than sufficient. I am on the fence about this as anecdotally I have seen people stretch for up to a hour per day and achieve very good results. I’ll link some peer reviewed guidelines in at the bottom.
While it would be academically great to do level 2 or 3 yoga positions, I don't have the time (I would need to spend hours each day to get that flexible if it is possible at all). Also I realise that maintaining flexibilty is something to work on for old age. What are the recommendations beyond "just stretch"?
While I am not a big advocate of stretching (without a activity based reason for it), I would stretch certain muscle groups as they are either not used in a full range of motion (potentially leading to inflexibility) gastroc, soleus, hamstrings, quads, gluts / glut med, adductors, hip flexors; Or muscles that are held in static postures for long lengths of time, back / pelvis muscle groups, chest and shoulders (cycling is very anterior biased).
General guidelines are (to me these are not entirely correct - but are written in such a way to be applicable to everyone); for your case, I'd go daily, x3 daily, 45-60 secs per stretch, x 3 times and till it hurts (minor pain but more than discomfort), in a sauna is sensation, hot bath or shower, post non-fatiguing exercise (vigorous stretching fatigued muscles is potentially dangerous).
American College of Sports Medicine (ACSM) Guidelines for flexibility training
Activities: Perform a general stretching routine following exercises that have warmed-up the body, targeting the major muscle and/or joint/tendon groups using static (non-bouncing) techniques
Frequency: At least 3 days per week
Intensity: Slowly stretching to a position of mild discomfort
Duration: Hold stretch for at least 10 seconds, working up to 30 seconds
Repetitions: Perform each stretch 3-5 times
http://www.acsm.org/about-acsm/media-room/news-releases/2011/08/01/acsm-issues-new-recommendations-on-quantity-and-quality-of-exercise
http://www.humankinetics.com/excerpts/excerpts/the-importance-and-purpose-of-flexibility
http://www.ausport.gov.au/__data/assets/pdf_file/0011/490979/Fact_Sheet_-_Flexibility.pdf
