Just like car insurance many companies apply an excess charge to any claims. This varies from company to company and some give you the option to pay a bit more have their annual holiday insure for travel insurance policy excess free.
You are just as likely to have an accident or become ill on a foreign business trip as a foreign holiday. However many take business trips alone and do have the support of a family around them should they become ill. At least with annual holiday insure for travel insurance you will have help at the end of the phone and be covered financially for medical treatment.
Most annual policies only allow you to travel for a certain amount of days per trip, normally 30 days. If you intend to travel for a longer period, even if it is well within your policy dates, you should buy a policy that allows extended travel periods. This may cost a bit more.
If you intend to go backpacking for a long period of time you should buy a travel insurance that reflects this. Annual travel insurance policies tend to allow you to travel as many times as you like during your year, but only for a limited amount of days per trip. These periods of time are no normally long enough to cover backpacking trips.