Absolutely, Yusef, but in the absence of any other figure......it will not be far adrift? I often have a look at max cruise altitude before push-back.
I'm (obviously) not sitting in the cockpit right now, but I recall the trim scale has (had?) MAC points on it that you could use in the cruise?
For Killroy - be aware that your company SOPs should dictate what you do. A lot of companies say to leave the perf init value alone, although it will (always?) improve cruise altitude and therefore fuel burn if set away from the 'default'. If in doubt, ask 'the mangement'.