Licorice as a sweetener which raises blood pressure? Excellent. My BP is typically around 80/50 (at its best) - needs all the raising it can get.

Any idea re: how long lasting the effect might be? Or should one not intentionally try to raise BP in such a way - or at all?

Chronically low blood pressure is indicative of poor adrenal function. Licorice builds up the adrenals anyway, which will help bring the blood pressure up to normal range. As long as you maintain the adrenals, which can be done through a variety of ways your blood pressure will remain normal.

When they say licorice root raises blood pressure they are really referring to the steroidal component of licorice root, which causes potassium depletion and sodium retention. This though is what takes very high doses over 6 months to cause this problem.