It's different for everyone and it depends on what you've been doing. If you've been reading a lot or driving or watching TV, etc., it can get worse. Maybe you've had ptosis before but haven't noticed. I had it my entire life and didn't notice it until I was 41 years old!
If you are overall weak, ptosis will get worse. You are using up the muscle gas (acetylcholine) that you need to keep your muscles strong when you do anything. You don't have to be "using" the muscles around your eyes in order for them to get weaker. Your acetylcholine "gas tank" gets lower and effects all your muscles to varying degrees. Make sense?
If you are worse, you should tell your neuro about it.
Annie