using desde with only the present tense

Question

On all the other sites that I have read, you conjugate the verb in the correct tense when using desde. Can you please clarify this for me? I read in the comments that the tendency is to use the present tense, but why do none of the other sites say this?

Answer

Hola Kerry 
As we don't know which other resources/ sites you've seen I'm not sure, but the most natural way to say that you've done/haven't done something since (time) is by using the present tense. You may see it occasionally using the perfect tense but it's not the most general usage. 
I had a quick look at other resources that coincide with this usage (present) and here are two other examples:
source one
source two
Saludos