Jorge Jesus' men top the table by seven points and with just four matches to play, are all but sure to be champions of Portugal for the first time since the 2009-10 season.
Jesus will be wary of a repeat of last season, though, when a shock draw with Estoril and a last-minute defeat to Porto in their last three games saw them lose the league by a point.
If Porto winning the title in such dramatic circumstances was not enough, Benfica then went on to lose the UEFA Europa League final to Chelsea before Vitoria Guimaraes shocked them in the Taca de Portugal final.
The upcoming close-season looks like it will be much happier for Benfica however, after their latest win saw them put even further distance between them and second-placed Sporting Lisbon.
Spanish striker Rodrigo gave Benfica the lead after 17 minutes before the man who set him up - Nicolas Gaitan - got on the scoresheet himself.
Gaitan met a loose ball at full speed and hit a 20-yard left-foot volley into the bottom-left corner, giving Rio Ave goalkeeper Ederson Moraes no chance.
Oscar Cardozo sealed the win with 13 minutes left, slotting home a penalty after Maximiliano Pereira was brought down in the area.
And another spot-kick from Cardozo in stoppage time sealed Benfica's comfortable win - their ninth straight Primeira Liga victory.
Rio Ave remain 11th in the table after their five-match unbeaten streak was ended, and had Marcelo sent off in the dying stages for a second yellow card.
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