Question: I've just remove my mudguards from my Ti frame and as usual I have put the bolts back into the frame where the thread goes into a tube - for example in the chain-stay bridge and brake bridge.
I used anti-seize on the threads and did not do them up tight.

Should I be doing this?

I do it because it looks a bit neater and I suppose to stop water getting int but I thought that maybe I am just risking ruining my frame if the bolt gets stuck in there.

Thanks

Answer: 
I usually plug the hole with appropriate size hardware. I add a dab of anti-seize compound. My reasoning (other than appearance) is that while the frame is aluminum or carbon the threaded insert is typically steel and there fore subject to rust.
You should plug the with something for two reasons:

1) to prevent water ingress into the frame 

2) the brazing or frame threads are usually bare metal so they will rust easily

It’s easy to put a bolt into them or a plastic or rubber plug (if you’re a weight weenie)