Yup, it's a one shot deal, mostly. That said, as the parent post mentioned, the cost of all those servicing missions was very high. It actually would have been

Yup, it's a one shot deal, mostly. That said, as the parent post mentioned, the cost of all those servicing missions was very high. It actually would have been cheaper, overall, to just launch a new one, or several. However, because of the weirdness of the Shuttle program, most of the actual cost of the Shuttle missions to service the Hubble weren't charged against Hubble's budget (substantially because the Shuttle program was looking for reasons it was useful). At nearly the full cost of building the Hubble itself per servicing mission (about $1.2 billion plus extras per flight) it really didn't make any financial sense. And now that the Shuttle program is over, it wouldn't be a factor anyway. Putting the JWST in low Earth orbit wouldn't make it any easier to be serviced, since there are no vehicles capable of servicing. But it would make it impossible for it to do it's primary mission. Moreover, we've gotten a lot better at building spacecraft and space telescopes since Hubble was constructed, most likely JWST will do just fine.