Hey! It def depends on personal preference but we try to keep ours open the maximum (2 years). 

I like doing 1 year, so that guests who enjoyed their stay can rebook for next year. Make sure to increase next year’s prices (I use a setting in price labs to do this), so you can account for inflation.

I typically leave mine open for 12 months out. Although this totally varies, depending on market, some people do like to book that far in advance. 
 

I've never really seen a downside of doing this, outside of making sure that you're keeping on top of your pricing. 

The experts that I watch/follow are saying at least 12 mo. - I use 12 and considering going further out.

Usually 12 months unless there's some particular reason I have to only have it open for a shorter window.

I go with 18 months, which allows those ‘planners’ out there to book their vacations over a year in advance.   I use Pricelabs, and enter a 30% pricing uplift for anything more than 9 months out, in consideration of potential operating cost increases.   

I’d say less than 5% of my bookings are more than a year out.   Those who book more than a year out are typically booking for a big event, such as a big fishing tournament, sporting event or concert.   

I use 2 years, and use PriceLabs to make sure that my “far out” prices are increased. There are several events in our area which typically sell out quickly, so I adjust those. I’ve made ours 2 years for two reasons: 1) I easily can with minimal risk 2) our competitors either can’t or don’t.

I go with 9 months.   I hesitate to allow bookings for a year out, as there as so many independent variables that can influence pricing more than a year out (the economy, new events in the area such as concerts, sporting events, etc). 

I do gather contact info for the majority of guests, and encourage them to Direct Book through me in the future, which reduces their costs and allows me to increase their ADR while not increasing their costs.