xanth basking
i dont think there is any hard and fast rule about how long they should or will bask. they all have different metabolisms and different personalities. as long as their supplemental and enviromental parameters are in order, they are perfectly capable of choosing the appropriate basking time.
specifically, what kind of basking lamp are you using? you referred to it as a "heat lamp", which sort of implies infra red. imo, an infra red lamp is not a good choice as a xanth basking lamp. it produces too much heat over too wide of an area. you dont want to heat the entire top of the cage, but rather a zone about the size of your hand. in addition, the purpose of basking is not only to produce localized, controlled heat source, but also to provide uva, which an infra red bulb does not do.
uva is thought to help curb depression and stimulate appetite.
how do you measure your basking temps ? xanth basking temps are pretty critical, depending on how you measure your temps, its quite possible that they are significantly higher than what you think they are. if you are using an infra red heat lamp, i would recommend switching to a ordinary incandescent household clear or cool white bulb of the minimum wattage required to reach the desired basking temp which i would limit to 84*
depending on your placement, cage size, and reflector.
25watts is usually plenty, 40 watts is usually too much. my personal recommendation for monitoring cage conditions is the $20 zilla therm/hygrometer with 2 seperate probes for temp and humidity. that way, you can place a temp probe right in the sweet spot of the basking beam. this is important since temps just a few inches away, can be significantly different. no nightime heat, if you can , try to offer a nightime temp drop of at least 10*lower than your ambient cage temp.
i wouldnt worry a whole lot about humidity, as long as your animal is healthy and your cage is well planted and has wet foliage several times a day, you should be fine. youre biggest risk as a new keeper, is probably over-supplementation, or too narrow of a diet(too many crickets)but those are 2 extensive subjects which i will save for another time. jmo