Re: It has been ten years since I have seen you
Micafe, your examples are an excelent combining "desde" with "hace"; still I think his attempts are very good too. I find it quite natural to say, "Hace diez años que no te veo."
Espanol3200, it would help a bit more if you notice that "desde que..." and "hace +cantidad de tiempo [que]..." are not the same kind of phrase; "desde" is a preposition, "hace" is the impersonal conjugation of verb "hacer".
Hace (verb, "it makes now") diez años (direct object) que no te veo (attributive clause saying something about the D.O.)
[Ya] son/van diez añosque no te veo /sin verte.
Llevo/cumplo diez años que no te veo /sin verte.
Han sido/pasado diez años desde que te vi la/por última vez. <—Almost literal.
Please, bring my mistakes to my attention. That's the main reason I dare to write my posts in English.