We are getting off topic here. The question was K-30 for back up with K-1, and the whole changing lenses issue. These are personal preference types of question. I frequently carry a long lens in a holster and a second body with a wide angle or normal lens around my neck.
While I appreciate Fenwoodian's enthusiasm for his K-1 it took me about 20 minutes to disprove it.
Having set up my K-3 with a DA*200 ƒ2.8 and a K-1 with a Tamron 300 ƒ2.8, shooting for the same DOF , shooting Blu Jays from my blind, the K-3 out performed the K-1 in every conceivable way. Subject detail, noise, colour rendition. And the weight penalty for using the K-1 and 300 2.8 is 4.5 pound. Not to mention the practical situations like the burst rate making image acquisition twice as fast on the K-3. That's very important with small birds where a "pose" may no last more than a second. The was virtually no difference in speed of AF.
So folks like Fenwoodian may have owned a K3ii, but they didn't make full use of it's capabilities. That's the only way they could make a statement like that. My feeling has always been, keep your most recent camera as a back up when you buy your new one. Otherwise you're a drop away from having no camera for a few months.
My test
I did some testing today... tripods set up maybe 2 feet apart both in the blind, taken at approximately the same time.....
One taken with the K-3 and DA*200 ƒ2.8
One taken with the K-1 and Tamron SP AF 300 f2.8
To normalize DoF, the K-3 was shot at ƒ5.6 and 400 ISO
The K-1 was shot at ƒ8 and 800 ISO
The surprise from that was the K-3 had better noise and contrast.
But enough of the web sized comparisons what about the pixel peeper you all say.
The K-3 produced more subject magnification and a cleaner image and more vibrant colour. Not what I expected.
OK, so it's only one test... but, so far in my testing.... 1 for the K-3 as a birding camera, 0 for the K-1.
But I digress, this thread is about a K-30 for a back up. I'd say go for it. You won't get enough money to make it worth your while to not have a back-up, or second camera to take to the field. With only one camera, you re always a drop away from having no camera. I always save my newest older camera as a back up, when I buy a new body.