Merme, one thing you want to know is just like any other forced
spring bulb that you buy in
flower (tulips, etc...) they might take a year or two to get back to its annual blooming cycle. It takes a lot to push out a
flower before it's supposed to come out!
Traditionally, Easter lilies were Lilium longiflorum, but I'm not sure if those are still being sold when you get an Easter
lily. Lilium longiflorum is hardy to
zone 7b. I'm not sure if Maine would be too cold. If it's too cold, you'll have to overwinter it inside like you do with cannas.
growing it in the ground will give you a 'bigger' plant but in a container you get more control as to when to force it into dormancy. You have to repot in a bigger pot most likely if you see rots blocking or coming out of the drainage holes.