it's gonna get worse because I think when LO gets older they think being with the other parent is like being on vacation. They usually, from what I have observed with family and friends, will try to take advantage too; make the other parent feel guilty and therefore 'ask' (can't think of the right word) to be spoiled.
As someone else here said, in the end, it's the parent who sets the rules and is there through thick and thin that gets (or should get) the respect and love.
As long as you are a kind and loving parent, try not to worry about what the other 'parent' is doing. However, if you think the spoiling is really affecting LO at your place, mention it and ask him to cool it a bit!