depends on what you mean by partying...but either way, i don't see a problem with it as long as it doesn't involve heavy drinking or hard drugs.
don't think for one second that this whole "act your age" adage means that you have to comform. it's just a social tool to control people with shame for not being cogs in the machine. it has no real meaning to it.
lets examine the next stage of our life: our 40s and 50s, where "acting our age" means having a fat gut while developing diabetes, man tits, low T, and erectile dysfunction, while being henpecked by a toxic nagging wife who is on the verge of divorcing you. does that sound like a good idea to you? personally I do not plan to act my age and develop diabetes.