I confess to being a little confused by the question. I don't attribute "bite" to burning characteristics at all. I attribute it to smoking approach (on the part of the smoker) and the inherent characteristics of the blend being smoked. That is, some blends, no matter how you approach them, are going to be easily provoked.
If anything, a blend that's been jarred for a year might be a bit drier than a fresh tin -- although not necessarily -- and that will only help to reduce bite. (Overly moist tobacco that bites will bite more than if it were drier.) In fact, in my experience, age only serves to mellow and enrich blends.
Which specific Virginia/burley blends are you having trouble with?
Bob