As I understand it, the recent expansion of the BigY to the BigY 500 is an important advancement by a more comprehensive assessment of the Y Chromosome. The more men who participate, the more likelihood of identifying more recent SNPs. While it is possible that you may not gain further personal information right now, your entry, combined with an increasing number over time provides the chance for new discoveries years from now. Since I attended the FTDNA conference in Houston last November, it is my understanding that it is important for all that more data to be added.
It also depends on your relationship with a surname group. If there is robust participation, with some well-defined Haplotypes, a new SNP can be useful. In the Beasley Project, we have two large Haplotypes that have confirmed ancestors born in the 17th century. We now have a Y-500 test for each group. With the expense of getting new people to Y-67 or Y-111, we can often use a less expensive test to confirm suspected lineages. If there is weak evidence of a connection to a specific lineage, testing for one SNP can confirm. If there is a new surname participant who is unknown, testing for two SNPs can answer "is it one of the major Haplotypes or neither?"
The Taylor Project at FTDNA is very large with many STR Haplotypes and, apparently, a fair amount of SNP testing. If you are financially able and willing, you might consider it. I would suggest asking your Taylor Group admin for recommendations for what would advance the project. As a group admin, I would be pleased to have that contact.