Looking for experienced based opinions on zero turn mowers. I currently have a John Deere SST18 with about 400 hours on it. It has been a great mower and taken a hell of a lot of strenuous use. My 2 acres yard is on very hard clay. Rolling the yard is more like taking the roller out for a bumpy ride. In addition my house in built on a steep slope so part of the yard is sloped is steep. The only reason I am looking for something else is that I would like to reduce my mowing time and before long I better plan on mowing my parent's place next to me as well as my own yard.

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Current:
1985 300D aka Miss Margaret
1991 300SE aka Alarice
1995 SL320 aka Samantha
1997 K1500 Silverado
Past:
1999 E300 ex-wife got it and let her son ruin it
1984 190 2.3 ex-wife got it and let her son destroy a great car
1985 300D (CA version) aka Maybelline lost to deer at high speed.
1981 300D aka Madeline (went to salvage at near 400k) rusty, yet best car I ever drove
Wishlist:
McFarlan TV6 (only a few privately owned)
ReVere with Rochester engine
1917 Premier (only one left)