Timber lintels

[Evren]

Hi all , I have 2 timber lintels above doors on the ground floor of my house with solid 1.5 foot thick walls. Over the years there has been some damp issues in the house which have also affected the ends of the timber lintels as they look rotten at ends.
My question is at which point do you make the decision to have them replaced ? And do you replace them with timber or other material ?

 

[^woody^]

at which point do you make the decision to have them replaced

Any time between now and when the wall above starts to crack.

Timber, concrete or steel replacements