interesting situation

ok, so i have this... situation:

let me preface this with, i LOVE our fvv. he's awesome, but i don't think i could live with him for an extended period of time, mainly because i can't live with anyone for an extended period of time.

he's been having a trouble finding a permanent place to live that he jives well with and that's easy on his pocketbook, so he's been couch-surfing for the past month or so, somedays at my place and somedays at his sister's place and somedays (when he doesn't have work) he'll go down to eugene to visit.
he has also gotten a totally sweet offer to go to yoga teacher training (someone is paying for the costs for him to go. what?! that's 10 grand!) in the spring.
i have a feeling that he's going to try couch surfing until the training in april (?!) because he likes the money he's saving by not having to pay rent.
that's all well and good and what not, but i CANNOT have him staying with me off and on until then. i would kill him. for many reasons, one of which is that he can't make a decision and stick with it. the other is that i NEED my space. and when he comes here to surf, it's not like he's just bringing in a backpack with a change of clothes and a pillow, he's bringing in 4 suitcases and a guitar, so i essentially have no living room when he's here. and it's not like i have a 4 bedroom house where he would be in the living room and i wouldn't have to see him ever. i have a TINY 1 (ish) bedroom place. you'll see it and you'll understand why i couldn't have another person living here even if we were fucking and sharing a bed.

now, i am totally thankful for what he did for me when i got here and for helping me out the way that he did and for him introducing me to his sister who helped me out way more than he did, but (and i hate to think about it this way, but...) i need to know where or when that obligation is fulfilled because if i don't draw that line, he will, unintentionally, take advantage of it and i will start to resent him because i won't know how to articulate that i feel like he's taking advantage without seeming hurtful.

if i had all the room in the world, he could stay as long as he wanted because we wouldn't have to cross paths. but i don't - i have a 450 sqft. apartment that could be considered too small for even one person if i had a "normal" amount of stuff. i have to tiptoe around when i wake up in the morning and do my morning stuff because i worry that i'm going to wake him and that makes me grumpy because it's MY FUCKING HOUSE and i shouldn't feel like i have to tiptoe! :)

and all of this comes out because he just sent an email again tonight asking if he could surf tomorrow for an indeterminate amount of time.

i said yes, but i don't know what to do or how to draw the line. what do i say? "you only have 4 more days of surfing for the rest of the year before i start saying no."?