With a one-time purchase of a license you will receive a perpetual license for the software, as well as license support from Atlassian for one year, which allows you to send support requests and update the software. After this initial support period has ended, you have the option of extending the support, you will find the costs in the tab "Optional extension". Read here whether you qualify for academic licenses.
You may work with your existing license as long as you desire. If you would like to continue to benefit from updates and the safety patch after the expiration of the one year support contract, we recommend to extend your support.
Remote agents and local agents
Other than other Atlassian licenses, Bamboo is not geared towards physical users, but towards development capacities within the system, so called remote user. The more agents you have, the easier you can divide long test scenarios into parallel running batches and simultaneously run multiple builds. The more builds you use simultaneously, the quicker your team will receive feedback to the changes made (and the quicker you have the chance to resolve possible problems).
To find the optimum number of remote users, you should inquire the frequency of committed changes, the amount of build plans and the duration of the plan.