Well i dont think thats the case, i told you i made 388 windows i used this

test {
var %i = 1
while (1) {
window -e @. $+ %i
echo -s Made window %i
inc %i

i changed it to window -ed @. $+ %i
and just went to 426, ok there not channel windows but the number of windows doesnt appear to be the limiting factor so im assuming its some resource that runs out.

lol i just did it on a win98 pc with 64meg of ram , and its still going 1000+ and counting (-ed option)