First batch of Geordie Mild is in the Corny and has been maturing for 4 weeks now. It still has that familiar twang/yeasty homebrew feel to it.
I know that there are a couple of things Ive done that I shouldnt really have. Firstly this kit has been sat in my roof for about 3 years, and was 2 years out of date

As Ive now been able to visit a homebrew shop , and for my next batch , have used an in date coopers ginger beer kit, and brew enhancer instead of sugar. This is now fermenting away nicely,and I cant wait to try it.
Im hoping that a longer maturing phase will help remove the homebrew taste, but Im not sure. Im currently using a 25L wine fermenter, as I can then just connect a pipe to the tap on the front and easily transfer to a pressure barrel. The plan is to leave it in the fermenter for a week, then in the barrel for 4 weeks, and then when its ready to drink, transfer to a corny keg, so that I can control the Co2 getting in easier, and ensure that it lasts long enough without going off. It also means as I have a couple of barrels I can be fermenting 1 batch, maturing 2 batches, and drinking a third at my leisure.
My main question is how long should I leave a kit to mature. Is 4 weeks enough? and what else can I do to help reduce or remove this homebrew taste.
Also, it turns out I didnt properly clean out one of the barrels when I put it in the roof, and after 3 years of drying on, the dirt is proving quite hard to remove. Any tips on cleaning out pressure barrels would also be appreciated, Ive left it overnight with VWP in and that took a lot off, but its still not 100% clean, and the top opening is too narrow to get your hand in, and the "barrel brush" I've got is no use to man nor beast!