I read a statistic (I can't remember the source, I apologize) that for lump sum vs dollar-cost averaging, dollar-cost averaging statistically only works better than lump sum if it's spread out over a period of 6 months or less.
For example:
Option A: Invest $12,000 on January 1.
Option B: Invest $3,000 on January 1, February 1, March 1, and April 1 ($12,000 total).
Option C: Invest $1,000 on the 1st of each month for 12 months ($12,000 total).
Statistically: Option B performs better by the end of the year than Option A. But Option A performs better than Option C. The advantage of spreading out a lump sum investment over a few months (Option B) ensures you aren't buying all of it at a peak. But, spreading out the investment for a long period (Option C) means you miss precious time in the market for most of the investment. So, dollar-cost averaging for less than 6 months is statistically the best thing to do when you have the means and are ready to buy.