My Chinese coach told me, growing up, playing with Friendship 729, just use a sponge and water to clean it every time. Once in a while use a little bit of soap but don't over do it. After 30 years, I am still following his advice.
My argument is, if the top sheet is really changing after you playing it so much, then the sponge is probably changing too. So by then, it is probably time to get a new sheet of rubber.
Also nowadays I use H3 neo. It is really not that expensive. I boost my rubber but after 2-3 months when the booster supposedly wears off, I really do not notice that much of a difference. I have a strong feeling that I just get used to the rubber by playing it 4-5 days a week so as the booster effects wear off, I dont really notice it.
I would change my rubber more often but I am just too lazy to boost. And the whole idea of ripping off the rubber after 2 months of playing to boost it again just sounds too much work for me.
So I do the above water/sponge maintenance every time I play and probably use a small amount of soap once every 2-3 weeks. And I just change the rubber every 6 months.