davno

[William Mahota]

As I vegetarian, I like to give my students the following minimal
pair:
Ja davno ne em mjasa. (and never will again).

vs.

Ja davno ne el mjaso (mjasa).
This is similar to Alina's example.
In these constructions, the present + davno implies that the action
will likely not take place again, whereas the past simply implies
that it hasn't happened for a long time. Of course, the past tense
could also render the English pluperfect in the appropriate context.
Others:
Sasha davno mne ne pisal/ ne pishet.
Ja davno ego ne videl/ne vizhu.

Misha davno ne prixodit sjuda / ne prixodil.
etc.
I'm not sure that semantics would allow all such minimal pairs
to exist, however, viz.,

Ja davno ne vypisyvaju Ogonek.  vs. vypisyval, which is clearly
a pluperfect in the right context. Of course, aspect plays a role
as well. Inherently perfective verbs of momentaneous action would
be used in the past, and I think that the imperfectives of such
verbs could not be substituted:
Eto davno ne sluchilos'.
Eto davno ne sluchaetsja.???

Bill Mahota