Originally posted by Jonathan Mac Invest heavily in APS-C lenses and you will make it economically unfeasible to move to FF. Problem solved
Though I'm reasonably young, fit and in good shape (reasonably...) the biggest problem with FF is the size and weight. I increasingly value the ability to have a camera that I can take anywhere with me, won't weigh me down and will be quick and nimble to use. Even the K-3 is too big and heavy for that purpose, so I use Fujifilm cameras which are perfect. Perhaps a FF mirrorless would fit the bill, if ever anyone makes such a system that appeals to me, but certainly a FF DSLR would be out of the question.
The grass is always greener...
On the contrary, I was quite happy for a few years using my FF K-1 with very small F-series lenses, including the 35-70, the 24-50 and the tiny, slow 80-200. Later, I added the 28-105 which is not that big, but my personal lens road map has no place for those beefy 2.8 zooms. Except for the DA 50-135, a masterpiece that keeps one of my feet in the crop camp.