I do auto renewal on both ferts and mowing. It is not part of my agreement, but I DO send notification both in the fall at the end of the season, then in the spring at the beginning of the following season, what the length of service will be, price, etc. So, there is plenty of notification, I think this is key. Otherwise, you run the risk of showing up at Grandma Lee's house and "Hey, I never renewed my service with you, get off my lawn!"
I don't think I will ever go back to the old "reply for renewal requested". People just don't get back to you, then you are left, nervous, wondering if anyone is going to renew their service with you. Not worth the heartburn IMO. On the flip side, if you assume someone does not want service just because they they did not reply to you, you run the risk of "hey, why are you not coming out to do my lawn, you did it last year?"
7x14 Stealth SE Enclosed with 48" side ramp
08 Toro Z400 48" deck, 21HP Kaw with EZ Vac twin bag
09 Exmark Turf Tracer HP 36"
21" Toro SR4 Super Recycler
Stihl KM90 Kombi w/ straight shaft trimmer & tiller heads
Husqvarna 125B Blower
Turfco XT5 Aerator
Turfco LS-22 Overseeder
I can do all things through Him who gives me strength.