For their sample period,monthly expiration dates were available up to 18 months into the future

问题描述:

For their sample period,monthly expiration dates were available up to 18 months into the future

对于他们的样本期间,每月到期日期是可长达18个月到未来

采样期间,有效期可长太(未来的)18个月
这里into the future不译出即可,因为18个月,已经含有未来的意思了