1. over the next 20 years 与 in the next 20 years 区别不大，均表示“在未来的20年中”。如：

Our costs escalated considerably over the next few years. 以后的几年里我们的花费大幅度增加。

Turkey is expecting an influx of several thousand refugees over the next few days. 涌入土耳其的难民预计会达几千人。

My reading of the situation is that this conflict is likely to get worse over the next few months. 对于这一局势，我的看法是今后几个月内这场冲突会愈演愈烈。

They have promised to pay the arrears over the next five years. 他们保证在随后的5年内偿付逾期债款。

Public spending is supposed to fall, not rise, in the next few years. 在接下来的几年里，政府开支应该会下降，而不是上升。

The company is on course for profits of £20m in the next financial year. 该公司有望在下一个财年实现2,000万英镑的盈利。

2. 用介词 for 也可表示类似意思。如：

It will stay cold for the next few days. 接下来几天天气会持续寒冷。

Winter produce will cost more for the next few weeks. 在未来几周，冬季农产品会更贵。

Meteorologists have predicted mild rains for the next few days. 气象学家预测接下来的几天有小雨。

3. 除此之外，还可用介词 within, through。如：

The family struggled through the next few years. 这一家人在接下来的几年里咬牙挺了过来。

I’ll have the report finished within the next couple of weeks. 我要在接下来的几个星期内完成这个报告。