how hard is to leave once there?

Depends on your economics and how much stuff you took with you that you feel you want to bring back. If you take all of your worldly possessions.....well, it's just as hard to leave, but only because of logistical moving problems again. If it's you, 2 suitcases and a plane ticket, no problem. Your income tax will mess you up, though - the IRS has one answer, the IRB a different answer. I am (still) trying to slay that monster now.

If you acquire anything on island you don't want to ship back or you have things from "home" you don't want to take back, have a garage sale.....it'll be gone before you know it.

This is why people are encouraged to put their things in storage for a defined period of time and reevaluate their life after 6 months, one year, whatever. I think the longer you can hang, the easier it becomes, so I'd say a minimum of a year. But it's tough enough to move one time - it's a pain in the butt and very depressing to do it twice.

If we had it to do over, we would have put our things that meant so much to us in storage and rented our home out under the watchful eye of our Realtor for one year. We had a lovely, more expensive home that would only have been rented to higher end incomes for our area - not to say the house couldn't have gotten trashed anyway, but as it was, our Realtor ended up buying a house and renting it to use when we returned because we had no place to go. Flip side is we were going to sell that house anyway, so the move to the VI just kicked that process into high gear at a great seller's market price at the time we left.

We had no anticipation of ever returning stateside, but things happen. You might not like it, or there may be some situation that arises that makes it necessary to return home. Give yourself an "out" if it's not for you or circumstances dictate change yet again.

It is easy to leave - if you have money, no encumbrances, etc.
We sold our house on StX quickly as we had priced it to sell and the market was hot and were lucky enough to have no mortgage, so we had cash to move.
We had enough liquidity to be able to move without closing on the house - we gave power of attorney to our lawyer on STX.
My husband is a health care provider, so got a position in the area we wanted to move to before we left StX.
We made the decision to have a gigantic yard sale and replace all our stuff when we bought again on the mainland.
We sold our 2 Island cars and shipped our F150 truck to Florida ahea of our move and arranged for a Ford dealer in Florida to pick it up from customs etc., service it, and hold it for our arrival.
We then stuffed our 2 cats in their carriers and flew to Florida!
That is how easy it was for 2 reasonably affluent adults with no real encumbrances. Now, if you changed any of the above parameters, it would start becoming a whole lot more complicated!!!! I realize that we are very fortunate.
This is just our personal story, but it might give a bare bones framework to tweak around to fit someone else"s personal situation.