These apparitions of Venus happen at regular intervals. *There is a
"resonance" between the orbits of Venus and Earth - 8 "Earth" years are
almost exactly 13 "Venus" years - so that conjunctions (when Venus
appears to pass between us and the sun [inferior], or on the far side
[superior] ) and elongations (when it appears to us at its furthest from
the sun) can only occur in one of five months of the year.

Interesting - by looking at fourmilab.ch/yoursky I looked at the
evening sky 13 years before several recent appearances of Venus and
noticed that it was there again, in a very similar position.
ISTR all prominent appearances of Venus being in the earlier part of
the year - February through to about June - would this fit in with the
elongations only occurring at certain times of year?

By late March it looks like Venus will be visible until 2230 GMT /
2330 BST - four hours after sunset and thus visible in complete
darkness for a good while.

Nick