Hmmm, I think I'd enable one timer set for 80% and once a week, and leave it plugged in. That should keep it from overcharging, and keep the car alive. But I don't think that 4-5 weeks is enough time to worry about anyway, so leaving it unplugged is probably acceptable, too. The only thing I'd be careful to avoid is leaving it charged at 100% for that long.
P.S. Another thought. If you set only an END time, it's supposed to start the charge just in time to finish at the end time. If the pack is already charged, it might just skip charging altogether. This would be ideal for storage since you would only want it to charge if the pack had discharged for some reason.
2014 Rav4 EV, Blizzard Pearl White
2011 LEAF SL w/QC, Blue Ocean, returned at end of lease