|Always leave room for expansion...|
The rooms were intentionally left un-numbered so I could make on-the-fly modifications to the map at the table. I also incorporated any changes made by a party directly into the current notes so there were names and stories to go with the bodies and bones scattered about the place. When someone broke a door, or removed a torch bracket or whatever, it became a persistent thing, something that affected whomever came next. That has always been one of the fun things I've liked about running this sort of a dungeon--the actions and choices of the player characters mattered and left an imprint, made a mark on things.
Now there were sections that did get repaired in-between player-character visits, and sometimes during a particular group's run. But that's something to deal with another time.
The nice thing about this sort of approach to a larger-scale map is that you can adjust to player actions and unforeseen calamities by just noting the coordinates of the last big explosion, runaway digging machine, or whatever. Wandering monsters can be arrayed along a range of coordinates so that patrols actually are on patrol, and so on. Doors and Obstacles can be relegated to a couple of simple random tables and noted in pencil (or with a tiny strip of Post-It Note). Prowling Beasts likewise can have a range of coordinates designated as their territory. And updating things is a breeze.
Another thing that I found really useful about this approach was that I would have a few unassigned one-page encounter matrices on-hand to slip into place for any area that the group moved into that I might not have been fully prepped for. Each block that was under exploration had its own page or two of encounters, notes, and traps so that anything could be modified or updated or vandalized by the players without it screwing anything up at all, for me. In fact it made the whole process of adapting each area to the on-going depredations and looting of the players incredibly easy. But it did wind up generating a three-ring binder to go with the map...
It was also a lot nicer to just map the thing out and not to have to worry about numbering everything. When you're numbering a map by hand sometimes you make mistakes. White-out isn't the most wonderful thing to work with, and this was before really erasable pens or some of the other fun office supplies that people take for granted now. And yeah, the damn thing is a bit on the 'Griddy' side of things, but it's from back before there was a Second Edition, let alone a Fifth...so give me a break.
In any case, the coordinate-grid approach freed-up more time to map-out sub-levels and to stock the dungeons and to come up with loads of fun new tables and special encounters. It also allowed me to drop-in sub-levels, portals, gates, or whatever with no trouble. Whatsoever. It worked. It still works.
There was also the added bonus that even when a player got sneaky and took a peek at the map, it didn't really help them. A couple of times I ran a game where the map was laid-out on the table for all to see. It saved time having to wait for the person trying to draw a map based on verbal descriptions, and cut down on the whole "You see a 20' x 20' room. There's an empty pie tin..." sort of crap.
One informal ruling that I also tried-out in those sessions was to allow anyone who wanted to draw their own version of the map -- but no tracing and no photocopying -- to do so and get to use the maps so produced in subsequent sessions. A few brave souls took me up on the offer. Most players balked at the prospect. It is always far easier to draw the map in the first place than to re-create it afterwards...