How can you appropriately use “延长”？ So， over the past hours, I‘ve been trying to figure out the proper usage of 延长。 I know that it refers to extending a period of time, but I'm trying to think about ways to use it (exact collocation) 
Could I say "延长到 （XX 时间） “ 
ex。 
比如说， 我们在医院等者， 我可不可以跟我旁边的人说 ”医生刚刚跟我说， 我们要等的时间回延长到两个多小时“ 

If not, how else could it be used?

Cheers,

Stephen
The usage 我们的会议延长了两个小时 is correct. When you want to say something was extended by [the extra time period], you use 延长(了)[time period]. If you want to say till what time something will be extended to, you use 延长到[time/date] or 延长至[time/date].

因运动员旧伤复发需要及时治疗，球赛将延长一个小时。
Due to the athlete's suffering from an old injury that requires timely treatment, the match will be extended by one hour.

Correction: boarding time is postponed rather than extended. Notice the Chinese word for postpone is 延后 not 延长.

飞机误点了，登机时间将延后至下午三点。
The plane is late: the boarding time will be postponed to 3pm.