Done

Done

The only way I see is to change them out 1 at a time. You can have multiple people on multiple anchors ready to install the new glue-ins, to potentially save a few nozzles. Then come back later to change out the other bolts.

If hanging on a single bolt is nerve racking, be on a rope that is clipped into a couple of bolts below you and have a belayer ready.

Or if you have the balls. On a belayed lead line clipped to the bolts below, set up a few hooks and hang on those.

I'm not sure how the rock looks like in your neck of the woods but does it have pockets which could accept Tricams?

Were the bolts originally placed on lead? If not then there is something at the top to hang off of.

If they were placed on lead, and there is truly nothing up top it gets trickier... Hang off of the anchors to replace the bolts along the route. Hang off of one at a time (backed up to the next bolt down) to replace the anchor bolts. Or replace on lead. Or find someplace on top to either build gear anchors or discreetly place bolts to have an anchor for replacement. Can even remove the bolts and fill the holes after using them if leaving a bolted anchor on top is a concern.

maybe climb a little bit higher to find a place to drill a thread? that might be a little more discreet than putting in another bolt

Go to the top and anchor in. Replace all the bolts below the anchor if replacing those as well. Return to the anchor and hang off a single anchor bolt and replace the other anchor bolt. Rap down and call it a day. Return once the bolts are set and replace the remaining anchor bolt.

If you are worried about hanging from a single bolt replace all the lead bolts and call it a day. Return once they are set. Clip into the last bolt and one anchor bolt. Replace the other anchor bolt. Call it a day. Return once it is set and do the same with the remaining anchor bolt.

This is a conundrum, and most often we employ two trips using one bolt at the anchor and the last bolt/placement as backup if nothing else is available. A newly installed SS Wave/Buhler bolt is about as good as it gets and hardly needs a backup on the second pass.

Another option is to drill a relatively shallow 1/2" hole(s) in an inconspicuous spot for a removable bolt (RB) from Climbtech as backup. No one will ever see a properly patched hole under a clump of rock rose, and you can angle the hole as to not tweak that sweet piece of gear. Kinda cheating, I know, but there is a serious backlog that lots of good folks are working to address. Safety and support of this work is paramount.

This is a good way to catch an STD!

As if you didn't already have one.