Beer will stay in the lines. The lines hold pressure. Beer will stay carbonated.
If you don't have the forward seal faucets you may have some between pour maintenance on the faucet to keep them from sticking. Otherwise, there isn't anything else to do unless you just drink extremely slowly.
Beween kegs is where the maintenance is. Many clean their lines after every keg and this is good practice. I am lazy. If kegs move quickly I may not clean the lines but bewtween the second or third keg or if there is visible sign of beerstone.
At that point, I also tear down the faucets and soak them in the same cleaner as the beer lines.
Depending on the length of your lines, it may be more effective to get a dish tub and soak both the faucets and lines. I have found this to be much more effective at removing visible beerstone buildup.
Of course, the more often you clean the less likely you will see buildup.
If in fact you are a slow drinker (say 1 or 2 months to kick a keg, or longer) then you'll definitely want to look into Forward Seal Perlicks. They will save you a ton of frustration.