You want to be sure the wine is clear and all the CO2 is out of it---on blackberry, this means at least 6 months as jp eluded to. I've been making wine 24 years, and have had the experience that 6 months can be too early because the wine still can have some CO2 in it. It's wiser to wait about 9 months. This also firms the flavor up better. I think it's a big mistake to manually degass fruit wines because you risk oxidation.
A big part of winemaking is understanding what is going on in the bulk aging of a wine. Most wines contain micro-debris of proteins and potassium, which precipitate out and produce haze. You have to allow enough time for these to fall out, or else your wine can cloud back up under storage conditions and refrigeration.
And if you are backsweetening, you need to use sorbate. And sorbate will not work until as many yeast cells as possible are racked from the wine. You go thru all the work and expense of making a good fruit wine--then you want to hurry the bulk aging step and run into problems. Don't be in such a hurry---the result of doing things correctly pays off in a nice, clear wine with no problems.