Personally i would be more worried about voidstones.
Because if youre really serious to make your empy to 99, you will form a ls and spam ***daily. As every run just need 5 mins, 12 1h, and spam like 3, 4 hours a day, it isnt impossible to net 100 hmp per day, taking 15 days to complete this stage, whats pretty reasonable if we think this game must have means to trap player for some time. Ot isnt impossible, 3h a day is a lot less than the time i spend daily farming souls.
But you cant spam endlessly due to lack of stones and voiddust being expensive and hard to find, limiting 1 6run each 5 day.
I think this challenge is suitable and feasible, just being capped by something stupid like stones is a pain.