Sony calculates the veteran rewards based on paid subscription. If you take a break (and cancel the account) you lose out on that time. Also, Sony hasn't been the best in tracking this either.
To add to Jigg's comments...
If you have 3 years worth of rewards, you can have up to 3 charactes with the rewards. So if you have only flagged two of them as veteran rewards, you can create a new character right now and flag them as veteran rewards, and the new character will enjoy all three years worth of rewards.