I'm sure you're aware that you can exit the practice session and change / adjust to your hearts content , more convenient than having to pit really.
Re your earlier comment on GT5 being tooo short , yeah , fair call on the A spec / B spec element but I believe online is where its longevity lies. Take a look at how many online tournaments and race series are currently on hold ! Racing people will always be heaps better than racing AI anyway
Track maker , photo mode and seasonal events also keep it interesting when you're sick of grinding for $$. Photomode is briliant , I've had a lot of people that aren't aware of the game saying how real it looks. One of the bits PD got right !