Russian Imperial Stout tastes too hoppy and thin

I have a Russian Imperial Stout that has been bottle aging for about 3 months. It's not bad but the hops are way too powerful and it just tastes kind of thin and is lacking complexity. Will that hop flavor diminish with time a great deal? Will I get a thicker and richer tasting beer if I just wait?

Nope. Unless it has strong alcohol flavors it's probably as good as its gonna get.

I disagree with the poster above to a certain degree. Some of the hop flavor will fade over time. If you used a ton of hops three months isn't really that much time. Will it get richer and thicker though? Maybe it will be perceived as this with a bit of diminished hop presence. Maybe not...

If you post your recipe I think people would have a better indication as to how it will turn out in the end.

As inhousebrew said, the hops will fade with time, though we don't know how much you used. If you hopped the living hell out of it, it will diminish but still dominate the beer. If it tastes thin now, it will likely stay that way.

You should have tasted it before bottling and adjusted it if necessary. I had a RIS a couple of years ago that fermented down too far and was too dry for me. I added lactose at bottling and it worked like a charm. Perhaps the best beer I currently have. I like my Imperial Stouts chewy, though...

The hop flavor and aroma should definitely fade somewhat, but if you find it too be too much now, you'll probably still feel it's too much later. As much as I love hops, I really don't care for hoppiness in stouts all that much, so I generally just add a bittering addition and leave it at that.

As for being too thin... has it carbonated fully yet? Flat beer can give the impression of a thin and watery beer. If it IS fully carbonated, it is, in all likelihood, an issue of mashing at too low a temperature. I would have done this around 155 degrees, if not higher. If you think you did, I would check your thermometer to make sure it's accurate. Now that it's in bottles you probably don't want to add anything to them, but maltodextrin or lactose are both good unfermentables that will add body.