If it's just spotting elk they should work if you go slow, but also dependent on what you're glassing into. If it's to size animals, I'd have a spotting scope as well.
Have you glassed something out to 3 miles before with the 15x and been able to decipher species/size etc. I agree with what CC11 says, finding animals will not be a problem so long as they are up. If they are bedded or in timber and or you want to decipher size then spotter would be beneficial.
Finding critters is easier with the binos…the conditions will dictate effectiveness more than the 1-3miles. For example, clear morning- no problem…..hazy day or smoky from fires or heat waves later in the day cut the effective distance. The conditions have to be just right for very long range viewing.
Spotters are good for counting points and evaluating trophy quality….and extreme long range scouting in perfect conditions.
I find myself very rarely using a spotter over my big binos.