3 miles? Are you taking a detour via Santa Monica? TBIT to T7 is about half a mile landside, a little longer-airside. So maybe 1.5 miles by the time you include getting to the Polaris lounge itself.

On the way over, split the difference - walk land-side from TBIT to T6, which normally has less of a queue than T7. If the line at security in T6 is long, then head on to T7. If you do enter at T6, take a hard left as soon as you're through security, then walk along the connector to T7.

On the way back you could do either, but the airside route is probably better. It is longer as you need to walk half-way along the T6 pier, go down, come back up in T4, then walk back to the front of the terminal again before continuing into TBIT - but it's a nice walk with pictures to look at along the tunnels, and most importantly it'll avoid having to go through security at TBIT which can sometimes be hell, even with priority.

Given all the talk above of distances, if you want to you could also catch one of the LAX inter-terminal buses from TBIT to T7. It'll probably be slower than walking for most people (depending on traffic and timing), but obviously less effort. Coming back I'd avoid the bus as it' needs to loop around the other terminals first so will take longer.