I've been slacking a bit with my Invisalign lately, how long should I wait to put the new set in?

I went on vacation a couple months ago and didn't wear my aligners the whole week. Since then, I've been slacking with my trays. I now wear them for about 5 hours during the day and when I sleep at night. I'm supposed to change trays every week but I've been wearing my current trays for about a week and a half now. When I tried on my next set last night, they didn't feel right. How long should I wait to change trays again? Any suggestions for getting back into the swing of wear them 20+ hours?