IMHO, you can always do just one end at a time.
It is not unusual for the usual OEM Boge struts to last 100k+, but they may not be performing a their best.
If it were my car, I would take this as an excuse to buy 4 Bilstein HDs, and enjoy the benefits on both ends for the next 100k.
Best of luck.
1986 300E 5-Speed 240k mi.