I just use my good bike.

What you need to do is get a routine for cleaning the bike. During rainy weeks, there is almost no point in cleaning the entire bike, so I end up just cleaning the essentials while cleaning the entire bike only once per week or once every two weeks. When I do clean my bike, the whole process takes me about 5 minutes. That is including cleaning the chain (but not lubing it, I do that before the next ride so all the degreaser is gone) and cleaning the rims, but without the soap bath some people like to give their bikes (jut a good rinse and wipe down).

I am not saying rainbikes are nonsense. Just that in my experience I have never needed one. If necessary I can just use a simple clip on fender if I wanted. But I do not need it unless I take a route where the the road gets muddy when it rains.

I have never felt that my good bike's components deteriorated faster from using it in all conditions. When you take care of the bike, cleaning, lubing, storing in an appropriate place and and replacing things when necessary, the bike stays in great condition regardless of whether you use it in the rain or not.