2 years back, i bought myself a new phone, a Motorola MotoX Pure edition, to replace my 1st Gen MotoX, which i had recently had a few issues with - it had twice in 2 weeks done a full factory Reset on it's own(which I later figured out had to do with how is sat in my pocket when crouching, oh well).
Around the same time My nephew's phone was having issues with it's battery(battery was puffy), so...did a fresh wipe, and gave it to him. he loved it, and it's been working fine for him all this time.
now, the MotoX Pure's Battery is getting bad, and i get the "new phone Itch" as it were, so i bought myself a Pixel 2, ordered a new battery and associated parts for the Pure, planned to fix it up, and pass on to the nephew, continuing the great family tradition of hand-me-downs, or in this case,"The Circle of Tech"
The Parts arrived yesterday, and last night I did a full wipe and reset, and then performed the battery transplant surgery, Following the first half of this video:
fast forward to today - they come down to visit this afternoon, and i get out the freshly refurbished phone for him, and my sister tells me "He just bought a new phone, cuz the old one died". I go out to the garage where he his working on a project with grandpa, and tell him about what I had planned on doing.... and he showed me what he got, some model of Sony Xperia. likely This one
had I known he was having issues, I could have done this whole thing a week or 2 earlier.... dang it! and saved him ~$160 to Boot!
Over the last 5 decades, I've worked out that it's pretty hard for others to understand what you are planning to do...unless it's on a Gann't chart, updated weekly, pasted to a prominent place on a wall, and emailed. Even then they don't understand what you planned to do.
Keep it as a backup.
A backup for you, or and make him aware that next time he has issues, he can hold that one while he gets hs other fixed (or you do it).