Thanks for the advice. While I've been home brewing for about 5 years the first 3 years I only brewed 2 different beers and it wasn't until I joined here in 2014 that I started to branch out into dry hopping, bulk priming etc. Only just added some steeped grains to a brew for the first time, pretty chuffed with myself actually. This question was something I hadn't come up against or read about so I wasn't sure what to suggest to my BIL. I knew you could lager for months but beyond that I had very little idea.
I did look up autolysis after MHB's post. You learn something new every day.
In regards to my BIL joining AHB I did suggest it when he started home brewing as I've always found it an excellent source of info. It's given me a lot of ideas and processes to improve my beer over the last few years.
No idea why he hasn't joined yet.
As to why he left it I have a feeling it was just a bit of laziness on his part. He's out in his shed enough fixing/installing stuff on his 4WD that he would have seen it sitting there every week and would have had time to bottle it. As I stated in my first post I did have a go at him about keeping better track of his brewing. I gave him a copy of my beer tracker spreadsheet when he started so he could track ingredients, costs, SG, ABV, SDs and a section for notes on each brew but he doesn't use it.
As for drinking VB after drinking home brew I have no explanation. lol. Each to their own I suppose.
On the bright side there's at least two people that understand what happens a bit better.
Suggested to him to taste it to understand what flavours come from leaving it for so long uncontrolled. Most likely he will tip it.