I guess everyone is different as I have never had that much of an issue with sweat in the gloves. My commute is 2 hours a day.
I do have several pairs of gloves though, the wife heard the term "gear ho" and looked at me with one of those faces
I have 2 pairs of Alpinestars SP-1s, a pair of Alpinestars GP Plus and the Alpinestars Jet Roads.
I do alternate what I wear so maybe that could be it but my oldest pair of SP-1s were bought in 2006 and I have never done any kind of cleaning and they still look and feel great.
To be honest (being the gear ho the wife says I am), if my gloves got to the point they were uncomfortable I would probably just get a new pair but again that is just me. The process in Vanilla's post is a good suggestion. Woolite is gentle enough on the leather yet should clean well. Just pick a leather cleaner/conditioner that dries well as some can leave your gloves greasy.