Depuis que, queries on tense of following verb

Question

I am puzzled why avoir is in the present tense. Does it agree with porter, present since glasses are still being wornDepuis que j'ai quatre ans, je porte des lunettes.Ever since I was four, I've been wearing glasses.
While savoir is present and dire is Passé Composé. I do not understand the patternNous le savons depuis que vous nous l'avez dit.We've known [it] since you told us.

Accepted Answer

Hi John,
The point here is that an "ever since" state situation is being described which uses the present tense with depuis que in French (as locution conjunction)   https://www.wordreference.com/fren/depuis
but it does translate as past tense in English, I suspect that this is the reason for your query?
There is no continuous present in French  --  the present is made to suffice with respect to your query about savoir.  The past perfect usage, later on, confirms the completed action (you told us)
Hope this helps?
Jim

Answer

Bonjour John,
Le Présent is used with expressions such as "être petit(e)" or "avoir ... ans"  because it implies a permanent/ongoing state rather than a one time completed action.

Depuis que j'ai douze ans, j'aime les romans policiers = Ever since I was twelve, I have loved crime novels 
Je connais Marc depuis qu'il a trois ans = I have known Marc since he was 3 years old

Le Passé Composé is used if what directly follows "depuis que" describe a completed one time action:
Depuis que j'ai fêté mes douze ans, j'aime les romans policiers = Ever since I celebrated my twelve birthday, I have loved crime novels
-> the twelve birthday was only celebrated once - therefore it is a completed one time action
 
To supplement Jim's answer follow the links below:
why not the present tense
can we say depuis que je te connais 
can the verb following depuis que be in the present tense
I hope this is helpful.
Bonne journée !