The limitations of what i feel comfortable in the field is determined by enviroment, work area and time to be spent on a particular job. Being tied up for long periods of time just adds to the workload and you will be putting off other customers that might have small problems like a battery, fuse or tune-up to get them back going.There have been places where i have rebuilt engines, replaced sections of mast rails to replacing wire harnesses. I try not to put off waiting customers and let the shop have the major repairs. Most places i go do not have a dedicated site that i feel comfy as to tackle a tranny build and such. I always let the customer make the call whether to repair on site or have picked up. If its a major job i will also mention it will require another tech and possibly lifting equipment. I know there are times when the unit can not be transported from site and no other option but on site repair. Nothing is worse than starting a complex teardown of a unit at a customer to find out you will need a steam cleaner, helping hand ect. It always seems to take twice as long to do a major on site job rather than in the shop due to not having the proper lifting tools or help available. Working out of a van limits what can be efficiently done on site and wasting the customers money on labor or productivity on down time is a bad deal for everyone involved. As the old saying goes " It takes months to gain a customer and seconds to lose them."