Hard to say.
It would depend mosly on 2 factors.Air has to be kept out(c02) or you could get some precipitation in the line and it could be a problem with clogging up the line.Though It will most likely happen anyway over the long haul,you dont want to be unclogging 30' of line every few weeks.
(2) weather the run is horizontal or vertical Obviously the horizontal run is going to experience settling much quicker than a vertical run.
Just make sure to try an keep air out and only dose when limewater is clear and your less likely to have issues with the lines clogging sooner though it will happen eventually,The strength of limewater is preserved longest ,weeks ime by keeping the air out ,so I dont think you should have any issue withit sitting in the line ,if you were refering to degrading.HTH