Spoons, slap that HH.357 on your Reo and you can say good bye to drip shields and topping off and extra bottles forever. All ya gadda do is squonk. That's what a Reo will do for you right away. The juice gets fed through the bottom threads so the only modification I can possibly think of is to widen the holes of the HH.357 with a hand drill, avid sells one, but I just use mine out of the box.
What an RDA/RBA will do is allow you to customize the best vape for you, which comes with a learning curve at first. The fine folks here have nothing better to do in life than to help folks like you 'n me get to where we wanna be so I expect you'll drop that HH.357 for an RM2 once you have the right coil 'n wick you can live with.
Asking how long they last is akin to asking how many hours of vape time ya get for each battery ie. really subjective but I'd say from listening to the reo-vets in the lounge you'll probably wanna recoil once a week, not so much out of necessity but for taste.
Just don't get discouraged, go at your own pace, because everyone I met in REOville who rebuilds, uses words like nirvana and heavenly, for a reason. Just be patient, have a backup, establish a baseline, and vape on! When you get there, document & collaborate so that others like you may get there with less trial 'n error.
superdrifter, darkzero, ehuman, pdib too many to name but these are the folks you wanna glue yourself to.
RHP