Quote -  Hey I only just realised I have render rewards from the last I think four months or something, does anyone know if it is possible to get them reinstated once they expire? Or should I just learn to keep an eye out on my account better?

Unfortunately once the render rewards expires, it's gone forever. I missed out on 2 such ones for a total of almost $20.00 :(

You should get an email notification when you get rewards.  Make sure your email address in your profile is correct and that you don't have mail being funneled into junk mail folder.

Also, they are issued on the 1st of every month. No harm in going to your account and taking a peek..

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi