lucapiegaia, as already mentioned, there's no set answer to this question that many ask.

I'm going to share my opinion by asking you a question back.

Are you going to change your own strings, or pay someone else to do it?

Here's why I ask; As GTA pointed out, it's hard to judge string breakdown as it happens, but when you change old strings to fresh strings, WOW, they sound nice. Sounding nice encourages me to play more, and that's the goal, right?

Strings are relatively inexpensive (in my neck of the woods anyway). If you're changing them yourself, you don't have much to lose. Change them after two months, and see what YOU think. If the change is dramatic to you, then change them again in one month, and see what YOU think. Find your happy place.

I will say that I believe that wiping down does help extend string life. Cleaners like Dunlop 65 Ultraglide, and GHS Fast Fret, also help in my opinion.