If you're here in Florida like my self, changing oil ever 25hrs probably isn't to often IMO. I change the oil and filter on my Kohlers ever 25 and the the mechanic at the shop recommended ever 50 with a good 10w30 but I wasn't comfortable doing that because of how much my mowers get used.
Most manuals will tell you to change your oil and filter (more frequently under severe conditions.)
The thing is you need to do(oil changes) and use what (oil) you're comfortable with, you know how and in what conditions your mower is run.