Hubble Space Telescope is a marvel of astronomical tools - particularly judging by how much it moved the science. It took a lot of fixes along the way, which certainly prolonged its useful life.
Its successor, James Webb Space Telescope, is going to be a significantly better tool. However, it's going to work only for a handful of years, and the reason is "we can't service it" (e.g., to replenish supply of liquid helium). It's going to sit in Earth-Sun L2 libration point, just a few times farther away from Earth than the Moon.
Why we can't service JWST with modern generation of spacecrafts able to fly farther than the Moon? Orion in particular could be a good candidate. Equip it with a propulsion unit - which would cost another launch of a heavy rocket and docking on LEO - and a airlock, which is relatively lightweight and cheap, and you can fly a few weeks mission. Similar capabilities are reachable by other spacecrafts (even with Soyuz, though I doubt it will logistically work to modify it for such an unusual mission). In exchange we'd get longer mission for such a unique tool as JWST promises to be.