I used to do a 5 minute warmup but after I replaced my 3rd motor due to oil related failures I changed brands of oil - and quit doing an extended warmup.

I don't know if either are actually to blame but it was a clear signal that I was doing something wrong so I had nothing to lose.

Now I start it and give it about a minute then go easy on it for the first 5 minutes or so. So far no complaints.