Burning faster than 4x causes coasters? What a load... tell that to all the people burning good quality media at 8x, 12x, and 16x even overspeeding in some cases. In most cases if you are using really old firmware for your drive you may not have media support for the media you are trying to use or poor support if the drive manufacturer didn't get a chance to fine tune the write strategy.
I'd, in most cases, say it's better to keep the firmware on your drive up-to-date. Other than that using good quality media (Ritek, Taiyo Yuden, Verbatim, Maxell, Made In Japan Fuji-Film/Sony, etc...) is the best way to avoid getting coasters.
You can't really do much about a coaster if you get one but if it's a video backup most computer dvd-rom will read a "coaster" well enough to transfer that back out to a new disc.