Saving the lot at a particular stage is a good practice... Exporting some back-up copies at the essential stages can futher avoid one to lose a lot. The lot files can get corrupted during a game crash... This way can further reduce the chance of losing a piece of hard work.

To avoid the killer done by HD death, backing up files in yet another HD and/or storage can further decrease the likelihood of loss.

Scaffolding is a good technique, but it has its own limitations like using up wall segments faster, making the game slower.
Indeed, one can start to delete the wall segments of the scaffolding to save the wall segment and the PC resources after tiling the necessary grid lines/rows... But before the wall removal, one has to do the level-tiling for the control area(s) and the working sites. The control area(s) hasn't/haven't to be connected but approachable to the working site(s) directly. Different control sites and working sites can cross one another as long as one has reserve-region to store the necessary height positions when necessary... Using the level-tiling as strings of tilings to play the music (to shape the building[s]). Just like how a musical instrument such as piano, harp, organ, etc works out its sounds...
The wall segemnts are to provide the simulated weight supports and to get the level grids out for the sacffolding, especially for the level-tiling (which is to provide a plain grid platform for the levelling tool to run on in order to shape the buildings)... Yet, there're some less used causes that I'm not discussing here coz they're further out of the scope.. However, some wall segments are advised to keep at the control sites.

Surely, those tiles used for level-tilings should be the ones you're not gonna use in the finalised lot unless you're sure their will-be-used areas have other tiles or closed borders for later switching or retiling-protection respectively. Also, it's a good practice to tile the ground with the same tiles for easy removal after the work...
So, it doesn't matter if the level-tiling be a mess after the work.

Also, the wall segment of the scaffolding should be removed from the highest down to the lowest because of the simulated weight support.

A full scaffolding is good for all-in-once control while regional scaffolding can save thePC resource at times... I do both ways dependent on which way seems to be more effective to me...
Say, if i've to eventually do the whole lot, I'll still choose a full scaffolding to save my effort not to get too bored...
If only afew small regions or a few levels needed to be shaped, I use the regional scaffolding or control column...
If it's just about 1 to 3 laevels shaped in curved ways, I'll use the ground directly...


For some of the points, I know they can be obvious to some experienced lot-builders and I don't mean they don't know, but I state them out for those who happen not knowing. I regard the infos I provide are for as many people as possible.