How to pass time on your military service

The recent string of coincidences which had lead to the TURNBULL/FAMILTON connection (still being investigated/validated) mentioned a few posts ago did lead to further work on my McEWAN relations.
This including catching up briefly with a fellow researcher of the NZ line.
It had been so long since we were in contact that her email address bounced, so a phone call later I was in possession of a new email address and a hint that she'd found James in the 1861 census in Glasgow, as a Chelsea Pensioner, and therefore on Findmypast's military records.
That was enough to set me off again.
What she didn't mention was that James was discharged from the army as "unfit for further service" and "not in possession of a good conduct badge".
These comments no doubt being at least in part because of his four courts martial (one Battalion, one District and two Regimental) and at least four spells of imprisonment, one for forty days. Two of the causes were unstated, but one was for absence without leave, and one for habitual drunkenness.
All in all, he spent 18 yrs and 177 days in the 26th Regiment of Foot, seeing overseas service in the East Indies and China (Wikipedia shows that this regiment was part of the first of the Opium wars in the 1840s, which would fit).
He was one of two James McEWANs from Perthshire of an age in Glasgow and I chased the other one around the records for a while thinking it was him (both had McCOLL connections, either by marriage or residence), even though he gave his birthplace as Port of Monteith instead of Kincardine.
Found that the wrong one's mother was a HENDERSON, and there were FERGUSON connections, which seemed a bit much of a coincidence, but I couldn't spot any links and went back to the miscreant James instead.