Your BFR can expire, but your US certificate will expire with it. When you need your US ticket again, within reason, you can retake your BFR.
It is my understanding that as long as one possesses a valid foreign (ICAO) license, the FAA certificate remains valid. Admittedly one needs to have completed a BFR within the past two years in order to exercise the privilege of the certificate, but to the best of my knowledge there is no requirement that a BFR be completed every so often (i.e., within a "reasonable" time) unless you are actually flying a US-registered aircraft.
In other words, if I obtain my FAR §61.75 certificate in, say, 1996, but don't complete a BFR at that time and don't get around to flying in the USA until this year, all I have to do is complete a BFR now and then I am good to go.
If someone believes the above to be incorrect, please let me know, and please advise regarding which FAR you believe is applicable.