In the longer game types (3 days or even 20/0 min) you should be making better moves, or at least moves based upon more analysis and understanding. So will your opponent, so things balance out.
But yes, I find that when I play a few longer games I'll often struggle in much shorter games, often due to time. So yes, I guess playing many longer games might make you loose some rapid games. BUT your chess skill will actually improve (by spending more time analysing moves in the longer games).
I also find that if I play many rapid games that my longer games (not really correspondance chess though) improve, as I am able to analyse the situation a bit quicker, but have more time to search deeper. Afer playing "too" many rapid games however, I find the quality of my games starts dropping
What I find works well for me is to play some 2/1 games (maybe 10 or 20 games, over a few days) but then play a few longer 20/0 games or similar. The short games train me to think assess and act quickly, while the longer games encourage deeper analysis and understanding
Just a question guys: does playing many online/long chess games hamper our ability to play rapid games? Because since I am playing 3 days per move games I found myself loosing too many rapid games (not especially here, but in other online chess sites)
Thank you!