If nothing about the physical situation changes, then the SWR will not change. But something might change in the long run, perhaps:
- Damage to the feed line (water intrusion, sun damage to insulation, chewing by small animals, etc.)
- Damage to the antenna (corroded junctions, parts broken off, wire fatigue).
- Plants growing near or on the antenna.
- Your neighbor erects a shed with metal (reflective) walls.
- The wire stretches or the mount points move
All of these things and more might at some point affect the antenna, such that you need to readjust it or repair it. Some of these are instant, some could take 10-15 years.
I don't mean that you should routinely recheck your antenna with an analyzer. But, if you think it might not be performing like it used to, or if something changed in its environment, then it might be worth checking.
Also, higher-than-normal readings on a SWR meter used while transmitting (whether built into your transmitter or in a separate unit) can be the first sign that something might have gone wrong, and you should check your antenna system for damage (or something else wrong, such as just not being plugged in).