I've done it before with good results. Main reason I avoid long stretches is because after a while they do more harm than good for my hair. Up to a certain point the shedding and breakage outweighs the benefit. But if I listen to my hair and act accordingly, a stretch can have leave me with increased thickness and the surprise factor. With that being said I'm going for a 4 month stretch. So next relaxer would be in September, just in time for a new semester and season.
My hair's BFF's for the next 4 months: a wide tooth comb + Satin scarf + Mane n Tail Detangler :)