The problem with term limiting is that you almost ensuring that people will not make long term plans which leads to drain of capital. This is also why for example the current Tier 2 Inter-company Transfer UK visa's are moronic, they force very high minimum pay (50K GBP or more per year) but limit the term to upto 5 years without any option to extend that duration or even switch to another UK visa (with the exception of marriage/partnership).

The idea behind the term limit was to make the local workforce especially in IT more competitive the result was that companies still bring allot of employees from outside of the EU paying them very high salaries, have those employees gain experience and then after 5 years take all their knowledge and capital out of the UK because they can't settle.

The immigration policy in the UK is one of the least efficient and most self defeating immigration policies I've ever seen, it's pretty much structured to shoot it self in the foot every time with idiotic regulations that do no effect those who actually cause the highest financial drain but disenfranchise those who could actually benefit the country.

The EU immigration policy could be more adapted slightly to be better, the general immigration policy in the UK really needs a rework, move to a point based human capital value approach as it's currently one of the few countries that actually would kick out some one who spent 5 years studying in the UK getting a master degree then offered employment with a salary of over 100K$ because they are not from the EU and do not want to provide hospice and nurse the elderly.