Are hot water returns worth putting in?
After doing a bit of research on what exactly hot water return lines are I found this page which goes into a lot of detail about how they work and their benefits and drawbacks.

The big drawback I see is that you will need to make sure that all your hot water lines are well lagged to minimise the inevitable heat loss that will occur with the hot water sitting in the pipes. Otherwise you will be heating water for it to go to waste when you aren't using it.

So you will need to add up all the costs:


extra pipework
lagging to minimise heat loss
extra redecoration where you've worked on the pipes
the extra heating costs
etc.


and decide whether it's a fair price to pay for instant hot water.

Another alternative would be to change the pipework so you don't have any long runs or even install secondary heaters for parts of the house.