Your plan
Your plan is a good one, and not that different from my own. I am concerned, however, that very far down the road, it may be difficult to find XP-compatible hardware; there are already issues with the newer SATA drives.
My plan is to get started building a spartan XP pro desktop that I'll only run occasionally. I'll run my repaired HP laptop for as long as it lives. With luck, that may be several years. By that time, I hope to have migrated completely to Linux, and I'll still have the XP desktop for my remaining aps that I can't get to run under Linux.
My MEPIS download is complete. Now to burn the ISO image onto a bootable CD, and hello Linux.
S