Consider that time Maya tells the story of Altair and Vega -- two starcrossed lovers who can only spend time together for a brief moment before being seperated again. That's Maya and Sensei. Maya went the dozens, if not hundreds, of version of Not-Sensei before a version of him became whole enough that he could accept the truth of their relationship, but then she broke.
Before that, Sensei had probably endured the same thing for dozens, if not hundreds, of iterations of Maya.
And before that, a different Maya...etc, etc, etc
This is why there are so many Mayas in Sensei's subconcious (the happy scenes), and Maya very likely has hundreds of different Sensei's in hers.