Normal
I check on mine off and on all day, when I'm home. I use a flashlight, but some, mostly slings, can't be seen without disturbing them. If I don't see one I assume its hiding and don't worry about it. But visual confirmation? Once a week for slings, usually the same for juvies, and every 2 weeks for big ones..but all my big spiders are right there looking at me, except for two burrowers. Feeding is when I confirm their health 100%.