[Rodger Knox]

For the OP, you should be fine with less tension.

In answer to tuning up and down, that depends. Some necks/tops will distort over time under string tension, others will not. It's a function of the wood from which the neck/top was made. My guess is there's a stress threshold for the onset of permanent deformation of the neck and top depending on the properties of the wood, the design, and the construction.

On some guitars, normal string tension is above the threshold, and they will eventually need a neck reset. Less tension would extend the time, but probably not indefinitely.

On other guitars, normal string tension is below the threshold, and they will never need a neck reset. More tension might make a difference, but it would have to be a lot more tension.

I'm assuming that this stress threshold varies widely from guitar to guitar, and the changes in tension due to tuning and/or string gauge does not push the tension above the threshold, or drop it below.
This is purely speculation, I have no measurements to back it up.