As far as sticks being bitter towards the end, most of the time it is due to high humidity. I live in a very dry climate and get the best results dry boxing my sticks for 5-7 days after rolling then at least a week in the coolerdor. A few months rest can make a so-so blend come around, especially when you use larger amounts of ligero I have noticed. A one week old stick wrapped in Sumatra tasted like grass/hay, two months later that same blend wound up tasting like cream and salted pistachio. I have learned the hard way that I really need to try and let a new blend rest almost 2 months before passing final judgement. The only exception to that so far has been my toasted marshmallow blend which is good fresh and doesn't change much at all with some rest.
The best advice I can give any home roller is to roll a metric assload as much as possible. Way more than you smoke and or gift to make sure you have a stockpile always aging. Too much is not even close to enough.