Regarding run time. I have the 21" push model (2101) and I get anywhere from 45 minutes to an hour of run time with my 5 ah battery. Note, my grass isn't really tough to mow so that may be a contributor. Plus keeping the blade sharp helps a lot. I keep the height setting at 2 and it cuts pretty evenly and has good suction. Moving up to 3 or higher and suction gets weaker for sure. Plus that $399 price for the 2101 with 5ah battery is a great deal right now.
The 5.0 should have more than enough juice for 1/4 acre lot. I have the SP an do not use it much because the mower is easy to push and maneuver. I have a 1/2 acre+ lot and can finish it with a 5.0 except on tough days (extra long or damp or both when I have let it go too long).
What kind of grass are mowing, how many days do you wait in between cuts. I have a 56 volt 7.5 ah battery self propelled. I live in South Florida have St Augustine grass, I catch my grass. I cut 7-10 days depending on the season, and never cut my grass in the morning because of morning dew. The mower does not like garden hoses, so I use my blower to clean the grass from underneath. Then wipe it down with a damp sponge. It’s a great mower!
If you have the same malady as I do, you need to look forward and get the self propelled.
It's a terrible malady, it's called aging.....every year I seem to keep getting older.
And, tho I liked it, I was never completely satisfied with the mower until I got the High Lift Blade.
Howard is correct, it improved the capabilities 100%.
And don't buy the "only for bagging" - I makes it mulch about 1000% better.