Never understood how non-stealth strategic nuclear bombers are meant to hit their targets without being blasted out of the sky before hand. Although, I guess if the first strike takes out radar installations, then there's no way of knowing where the bombers are, but otherwise it would be a case of picking them up on long range radar, burning through the jamming and directing the patrolling aircraft in.
I guess it depends on what range burn-through is achieved vs launch range of stand-off nuclear missiles.
Altitude would also help...but then again things like the MiG-25 were designed to get up to altitude sharpish.