Advice needed: patch, repair, or replace? (pictures)

[testpilot]

Hi everyone,

First time poster here, but hope my post fits in!

I recently bought a house that needs some TLC on the roof. 1/4 of the roof is brand new from the previous owners (due to a tree falling on it), but the rest is of an unknown age.

1/2 of the roof looks like this, which to me looks pretty good.

1/4 of the roof (Western side) has some signs of wear in spots:

The valley clearly needs some work, especially in the bottom 10 feet:

Questions:
Looking at the valley, is there any way that I can cover it in a couple coats of roofing sealer and hopefully keep it water tight for another couple of years? Or is it totally beyond patching at this point? For what it's worth, there are no visible signs of leaking presently.

Looking at the rest of the roof, is there any cause for concern, or reason to replace the shingles? I had a roofer come by and he quickly said the whole thing needs to be replaced - I knew he would say the valley does, but I was a little surprised that he recommended everything else be replaced - I thought the rest looked reasonable for the time being.

Any thoughts or opinions would be much appreciated!

 

[Burnerman]

You'll get a couple of years more with some bodge on there, but its surprising what nasties can be lingering under roofing felt!
The valley looks somewhat wet either side of it - is this just residual water?
The rest of the roof looks OK, and damage is often caused by a roof ladder.
John