The straight answer to "how long can I roam for?" is "as long as you want"!
I'm going to assume, although you've not said, that you're travelling abroad long-term and are planning to use inclusive or per-week roaming - and want to know how long this will last.
Within the EU at least, inclusive roaming is subject to the stable-links policy which broadly requires usage in the UK for 2 months in every 4.
Where are you travelling to, and for how long?
