Too many $_GETs?

Is there a point where a link in a PHP/MySQL-based site has too many $_GET v
ariables attached to it?

I use the format "index.php?a=1&b=2&c=3&e=4" to pass variables from page to 
page, and am wondering where the limit is on such a format. Right now, eight
 variables are passed, each being one to four characters in length.

It's the best way I know to keep varaiables alive from page to page in a sit
uation where the user does not use cookies, but I'm worried that too many $_
GETs will slow down the server, cause trouble with the page, and possibly ca
use problems that I have no
t yet seen.

Comments? Suggestions?

Thanks in advance for any feedback.
-v-