Spawn point = last bed you clicked on. You can only have 1 spawn point (bed) active at a time. Once you activate a new spawn point, the old spawn point is removed. If that last bed (current spawn point) gets destroyed somehow, other bed(s) will not automatically resume being a spawn point. You have to manually click on a bed to activate it.

Carry supplies to craft portal ( and keep a portal set up at home base) to avoid having to make beds out in the field and ending up resetting your spawn point. Any time you need to rest or sleep or even if you enter new biome and anticipate encountering harder mobs, place the portal somewhere safe nearby, and if you happen to die you will spawn at your base and have the means to portal back to collect your death statue without all the hassle of running back.