If I replace an injector liner with a new deactivated liner (packed with deactivated glass wool) do I need to disconnect the column and condition the liner at an elevated temperature with a carrier flow (helium!!).

I see no mention in literature.

Does anybody do this routinely?

We don't condition liners (we use SGE ones). I've never seen any 'liner bleed' at around 250deg C which is what we generally use. I'd imagine the suppliers give them a good roasting before they send them out and they pack them in heat sealed packs.
This is just anecdotal obviously - someone else might tell you differently.
John

If you try to condition a liner in this manner on a GC with electronic flow control you will get a leak error and shut down the flow. After installing a new liner and having it come to temperature I recondition the column for a few minutes to remove anything that bakes out of the liner. A solvent blank would serve the same purpose.

What we do is pre-condition the liners by placing a few in a beaker inside of the GC oven. Then, by the time we need the liners, they have gone through enough oven cycles that they are ready to use right then.