They aren’t falling out all the way but they do seem to be coming unstuck, usually after extended periods of disuse, they don’s seem to be particularly worn down, and I haven’t left it strung so I don’t know what it could be. I can usually push the unstuck part back in but it only stays in for so long.
Is it very hot and/or humid where you are? That could contribute to the pads falling out.
Do you lube? Maybe you got some lube on the response pad.
You could use some contact cement to hold it in place. You may also wish to try new response pads.
We’re just coming out of winter so it hasn’t been more than about 28ºC/ 82ºF (at most) so far, though I did have to put it in the freeze to get the bearing out recently. No lube Dry all the way 
I’ll probably end up replacing them. But normally I don’t replace my pads until they are so worn that they fall out 
If heat is a problem though I’m not looking foreword to actually getting into summer, we regularly get weeks that don’t go below 32ºC/ 90ºF and often hit 42ºC+/ 108ºF+ in the summer, but usually it’s fairly dry heat here in South Australia. It’s not like Queensland or anything, and even that isn’t quite as humid as Florida, so at least that’s one less thing I have to worry about
You may have just gotten some bad pads then. It happens.
You might consider using flowable silicone as your response system. It might be more expensive up front, but for the cost of 3-4 sets of pads, you can go and silicone 50 yoyos with a tube. Since there’s no adhesive to deal with, you don’t have to worry about adhesive failing. It is also very weather resistant, so that might do it.
Another option would be a #11 silicone rubber(Black) o-ring gasket, but you’ll want to shave that down and honestly, they kinda suck as a response but they seem to last darn near forever. It’s an option I don’t recommend.
When I was in Vietnam, I had a few sets of pads fail and I was only there for 2 weeks. One was a worn out set, the rest were in fairly decent shape. Heat and humidity had to be the culprits.
I also agree: there’s no point in replacing pads until they are “falling out”, or binds are just too slippy/sloppy to be of any use.
I was going to get some silicone but apparently the monkey snot had started drying up, and if I’m going to go the the effort of trying silicone I may as well have blue response to match most of my yo-yos I know it probably seems a little silly, but I really like blue
Keep in mind that RTV silicone(including flowable) has different properties for performance, which is true not only in their intended applications but also how it performs as a response system in a yoyo. There’s red, blue, black and grey, which you’ll need to shove into the response groove and then recess. Flowable you can just squeeze in.
Worse case is with blue is you end up not liking it and have wasted money. But, you could get the same results with red, black, grey or clear flowable too. It’s all preferences. Red and blue are fairly popular alternatives,with red being a bit more popular.
Some YYF pads (maybe me?) after time become solid, not completely but they aren’t rubbery.
Then they tend to fall out. The adhesive could be worn down as well…