To start off with , theres the surveying,( if a tower site is off by more than 6 in. there will be problems in alinement) Enginners also have to all the blue prints exact,or this too will throw off alingment . Sometimes the install crews can make on site adjustments, if not the part is sent back to be refurbished to exact specs.
The digging of the foundations for each tower,( having to carry all the foundation materails to each tower site)Having a helecopter avable to fly cement and towers themselves to the tower foundations,
(helecopter companies make more money flying water during forest fires.) Having all the differant parts of the lift shipped from around the country,the two major lift companies have thier manufactoring plants in Colorado, Utah, California,and eastern Canada.As well as Europe for the hual ropes, and not to mentione cabins for gondolas and trams.
Then the weather. When it's raining like crazy, lift install companys, don't want thier emplyees taking chances on mud roads, you can't get the crane up to the top when it's been raining for 3-4 days in arow. Plus is there the correct size of crane avabile to rent.
The electrical systems all have to be wired onto each tower, and tested before the inspector will pass it.
Computers monitor all systems on a lift,( the new models) electrcil, the motor that runs the lift, the back up motor, the braking systems, the spacing of the chairs on high speed lifts. And the actual speed of the hual rope. Temps of motors,etc.
Depending on the length of the hual rope, it has to be pulled into place,strung up, by the install crew. They have to go slow, so they don't harm the hual rope, as it is pulling along the ground. Once the haul rope is strung up, rigging has to be set up to set tension, then the splicing on the two ends of the haul rope can take place.
Once the termeanls are in place the welders move in and weld up a storm, welding the differant pieces together.
Once all the above is done, if the lift is on public land, the forest service has to inspect it, the county which it sets in. Then the load test can be completed.
Most resorts begin a yearahead in ordering a lift, so that the manufactor can build the parts for each particular lift. A lift at Deer Valley or Park City, looks the same, but they all have differant specs.
So, if you don't think it takes 5 months to build a lift, you can ak any one in management at a resort, or a Lift Maint.Tech.