Glass has to be clean to “work” just like a barrel has to be shot to have any fun. In both cases they age a little each time, just like us. The alternative is to not go outside, so, i keep lenses reasonably clean and beyond that don’t worry about it.
For light dust/field debris i use compressed air.
For mud splashes or an old used scope from a store rack somewhere with 1/32 inch caked dust, will swish some soapy water around on it, rinse, repeat as needed. Finish with lens spray and lens paper.
For general greasy prints or whatever, again lens cleaner and lens paper or clean microfiber. Don’t believe for a second that nikon cleaner is going to eat zeiss coatings. I don’t use much of lens brushes or cloths as often just because i can’t know they are clean, whereas lens paper always is.
I live in a dusty gritty place, so keep all this stuff in a lid container and ziplocks.
Most everything has scope covers.
Couple prepackaged zeiss wet wipes in pack, same thing i clean my glasses with. Don’t recall ever really needing them, but.
