They are easy to grow indoors and don't seem to suffer from a lack of humidity like many tropical plants do that need to be over wintered inside. I have one that I started cutting back when it hit about 5'. It branches but those branches will continue getting tall so I just keep on cutting it back. This past winter I stuck it in the garage and forgot to water it for several months. The garage is heated to just above freezing during the winter. Surprisingly it's still alive and is putting out new foliage now that it's outside. I've kept it in the greenhouse over previous winters and it does quite well. It doen't grow as fast but didn't drop it's foliage. I didn't want it taking up greenhouse space this past winter which is why it ended up in the garage. I'll continue keeping it in the garage but hopefully will remember to water it.

Thanks, perhaps I'll move it indoors. What about light? How much does it need?

I keep it outside in full sun during the warm months. From now on it goes in the garage with no light over the winter.

When I was on vacation in the UK I saw an Avocado growing in a backyard near a subway station called Baron's Court in the west of London. It was becoming a tree indicating that it was outside all the time however no flowers or fruit was present. Maybe you do not have to keep these trees under cover during the cooler months as London England is hardly what you would consider as Avocardo country. Global warming - who knows?