Don't have to work too hard, historically VGR typically hits 20s to 22s going into September and then hits its lows of 16s to 17s October through December.
If there are external economic/political factors then could be lower.
A buy in the 16s will provide a combined ($1.60 cash and 5% stock dividend) ~15% return excluding any future cap gains.
So there's 3 months after September dividend to hit a GTC in the 16s if you wish to collect the next dividend or 4 months if you want to gamble that it might hit the very low in January.
I certainly have proven to myself that I cannot predict the very bottom in any stocks price so I would be placing a GTC in the 16s if I wanted to add.
Disclaimer: my crystal ball isn't broken ... I never had one but ...
If I was trying to place a more exact time frame including PROBABLE external factors then I would say the NOV/DEC coincidence of normal VGR low price and the next budget fruhaahaa and year end tax loss selling.
PS Personally I am debating whether to execute my planned September runup sale ... not sure VGR will hit the higher end of its range (21-22) with all the current market volatility ... may just hold and wait for the Sept 2012 run.