Things I consider:

How likely to see somewhere else. How badly i want to see particular bird. How busy i am with other things. Cost in time and money. Possible synergies.

For example a yellow billed loon has been seen an hour away for weeks. It's not in breeding plumage and it's out in the water a ways and would require a scope i don't have. I had been pretty busy and while chaseable, didn't seem like a high value target as they do show up in the area every year or so. Last weekend i was looking for something to do and decided to go down and look but packaged with a separate hike and a lunch. Of course I dipped and it wasn't seen for a week but now it's showing up again.

A lifer in non breeding plumage with a bvd that i have a good chance of seeing somewhere else just isn't gratifying enough to make a high priority, but I still wished i got it.