What is the ruling on frequently repeating ablution — around 20 or 30 times daily — not for prayer, but with the intention of purifying oneself from sins, given the continuous expulsion of gas? And is excessive ablution of this number considered reprehensible extravagance?

Renewing ablution for every new event is a good deed, and it is hoped that by doing so, you will be among the purified ones whom Allah has praised. This is supported by the hadith (definition) of Bilal, who used to perform ablution for every event and pray two rak'ahs. As for renewing ablution, it is recommended if you have already prayed a prayer with the first ablution, even if it was a supererogatory prayer. In other situations, such as performing ablution and then performing it again before praying with the first ablution, this is not legislated.