You do have better control over the shift points, but need to pay close attention to the RPM'*. Maybe its just me, but with that kind of milage, I would baby that tranny a little more. The fact that yours is running strong at that milage without (I assume) being rebuilt it good news.
You said you want it to last five years. Don't get me wrong, its not going to fall out while you are driving normally, but these transaxles can't hold up to alot of abuse. Especially the older 60 series. A rebuild will set you back $1500 or more. You need to decide if beefing up the tranny is one of the mod'* that you want to pay for in the next five years.
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