Just in case it helps to know, I always get gas struts recharged rather than replaced. A guy comes around in a van with a pressure chamber. The strut goes inside the chamber, the ends of the chamber (tube) are sealed, and a nitrogen cylinder pressurises the tube to about 140psi, forcing nitrogen in past the strut seal. The pressure can be adjusted up or down as required.
I guess it must be possible for a strut to fail completely and suddenly lose all its gas charge, but more likely the pressure has fallen steadily over the years to the point where it only just does the job (or won't do the job).
I think you'll find that with the pressure replenished, it takes a long time to leak away again. Will probably last the rest of the car's life.
Cost is a small amount (the equivalent of about £15 for both struts).
Sadly, I don't know how you find this service locally (the guy I use covers a 50km radius, rather than the 18,000km that probably separates you and me).
-Alex