I just read Why do small transactions without fees ever get processed? and it made me wonder about the risk that a legitimate, lock_timed transaction might not be processed once the lock_time is past.

I'm aware (from the above question) that in the reference implementation, the increasing age of a transaction (in the mempool once it's been submitted?) should increase its priority regardless of the its fees but not every miner is willing to process low(/no) fee transactions even now never mind what they may (not) do in future.

So if I have a signed transaction with a (very!) distant lock_time and it has fees that were considered reasonable at the time that the transaction was created and then when I submit it after lock_time what is the risk that no miners will process it because its fees are subsequently considered to be too low to bother with it?