In the last 18 months, we have been very fortunate (in large part thanks to the strategies we have learned from some of the brilliant travel minded people on this forum) to redeem our points for the two of us to have gone to Europe and back in F, as well as locking in our next two holidays to Bali and the USA in F (well Bali is a mix of J and F). We've taken our balance down to ZERO as of 3 weeks ago.
Our goal is to get enough points in the next 12 months to be able to book our annual big holiday for 2019 (as the USA trip is the 2018 trip), or to save up enough in the next two years to do RTW tickets (F/R) in 2020 for our 5 year anniversary (marriage, not points hoarding). Not knowing what changes to the rules for redemptions will come down the line between now and then, we just shop/spend smart. Every dollar we spend has points taken into consideration. Did we get the highest possible number of points for that spend, without paying more. We don't carry cash, and any we do have goes into a jar and deposited in the ATM on the weekend, so we aren't spending without earning.
Previously, once we had a good balance, we start looking at what the current "fares" are, where that could take us, and start to make plans based on that. We monitor when we have enough (or when we can justify the spend for topping up the points, such as buying from Amex at 2.5cents per MR point is of value if we are going to be short but have a set date in mind that we want to book by).
We always are crosschecking each others spending.... Did you buy that on eBay through the Velocity eStore? Did you use Platinum Edge for your petrol? etc.
Now that we have both maxed out the Amex signup bonuses under current rules (it was good while it lasted), we struggle to find bonuses that are worth the application note on our Veda. But, since we have locked in fixed rates for the next 5 years for our house and investments, we won't really need to be impressing a bank for a while, so we can churn cards for the next few years.
The short answer is no set numerical goal. The goal is, see a point, grab it.