Think your mate isn't giving you the full story. Your runout date is your runout date ... leave before that and you forfeit your pension!
However ... by doing such things as saving up your remaining leave, using your termination leave and using your resettlement allowance to do work experience you can "effectively" leave 3 months early.
Be aware though .. you need to get permission for secondary employment for your leave period and resettlement period. If I recall correctly you are allowed to be employed during your termination leave with no penalty (apart from the extra tax!) Not sure about the rules regarding being paid prior to this though.
A lot depends on your situation and how your management decide to play it at the end of your time. I had been replaced and done a HOTO about 5 months prior to my runout date. Once I had de-kitted and done all the admin I was fairly free in what I could do. I still got permission for second employment and started my new job about 2 months before my "official" last day.
As I said earlier, check with the resettlement officer and the reams of documents they should have. Things may have changed since I left.
If you've got a job to go to, the Mob will let you go in your last three months, if it means that you would otherwise lose the job. You shouldn't lose your resettlement but if you've left it until your last three months you're cutting it fine. If you have your resettlement course in your last three months and you are to start new employment at the end of it, they'll let you go after your course. If you go before, you'll not get the financial support for it and you'll have to foot the bill for the course in its entirety yourself.
If they do let you go, it's a favour. You're not entitled to go early so don't try to shove it up their noses. I must admit that everyone I know who had jobs to go to in their last few months were allowed to go without any adverse affect to their pensions and gratuities.
1. As Biscuits wrote, gain agreement from your boss and remember it's a favour. I always ask my guys for their rough plan at 12 months and their detailed plan at the 6 month's point, so that I can judge whether I can let them go: it concentrates their minds wonderfully when they realise that I will let them out of the door a bit early. But I always insist on a mobile number and the ability to recall them in the event of a disaster. It hasn't happened yet but it will - one day!
2. No - you will not receive your pension and gratuity until the 22 year point - and until your unit has completed all the paperwork and returned it to Glasgow. That includes the details of your final medical.
3. It is also about this time that Records will spring on you the bit about you missing four weeks from your service history because you did 28 days in Colly or didn't join your unit until 28 days after enlisting. Don't ask me why they wait until this point to do so - I have never been able to wring a satisfactory answer from them!