Used to have that trouble running thru JG fittings through the cooler but since recently going to all quick disconnect not anymore plus I use silicone milk hose as beer line
And when the problem did occur it was over 48 hours not 24
It does in most pubs and any decent landlord/barman will pull a drop thru through, you may notice some "using it up" mixed in to the first few pints served, it will depend on the length of the run and how long it sits.
I leave mine in the line from one week to the next. I find there is a noticeable difference in the first and second pint so I tend to sacrifice one at the start of the evening.
Can't say I've noticed much of a problem. My beer line is 3 metres of 3/16" dia, but most of that line is coiled up in the fridge, so it stays as cool as the Corny. I sometimes go 3 or 4 days between pints but I've never had to ditch any yet. :party::party::pray::hat: