flying more than one make and model?

Hi guys, another question.

What are the most commonly-held views on flying more than one make and
model of aircraft?

Take the example of a 172 and a Warrior. Clearly the aircraft are
different and the best solution would be to fly only one make and
model, but the reality of plane rental is that if you are checked out
and current in more than one aircraft, you have more flexibility in
terms of when you can go flying, which means more fun and more overall
currency.

At what experience level is it generally seen as sensible to regularly
fly two different makes and models of plane? Is this a big deal or not?

Tom