Bottom ball joint bolts are fine to re-use, they have pretty much bugger all load given the arrangement.
Wot 'e said

It's not actually
holding anything on, in the same way as, say, the front wishbone bolt does - it's 'only' pinching around the vertical balljoint. The balljoint is held in by gravity/the weight of the car and if you were to run without the pinchbolt, you'd have to do some serious Pentii Airikkala action in order to relieve any unsprung weight on the balljoint, and in theory allow it to fall out - and even then don't forget that balljoint is the one that you have to often belt with a mallet in order to pop it out when replacing the wishbone, as it's tapered and a bit jammed in, through weight/age. Also, the recess in the balljoint shaft is there to accommodate the pinchbolt - so running with a loose pinbolt isn't unsafe
per se until the pinchbolt actually rattled free - then returning us to the Pentii scenario. It's a system developed over literally decade of design, and like so many systems, has a sort of in-built backup/safety margin. A bar with a split ring in both ends would do the same job.
Personally never replaced one, other than in cases of extreme corrosion, where my socket is starting to not grip as well.
EDIT:
Bottom ball joint bolts are fine to re-use, they have pretty much bugger all load given the arrangement.
The only two reasons for needing to replace are excessive corrosion and a boogered thread from removing the nut fully prior to drifting the bolt out...
Damn, must type faster!! Yep, precisely!
