The bobcat in heat sound will work anytime of year but as GC said Jan-Feb is their breeding season. During this time the toms are roaming looking for love and are very receptive to this sound. However don't be afraid to us this sound at anytime of year. I've usd it effectively just about every month of the year. Just last week I used it to convince a hung up bobcat into coming on in. In fact he came so good I had to use my voice to get him to stop for a shot.
Here is the bobcat from last week.
When using this sound don't be afraid to play it pretty constant. If you have ever seen a real bobcat in heat you will know what I mean. They (are at least the ones I've heard) are just like an old barn cat. They will squall and squall while in heat until they attract a suiter. Don't be suprized if you call in a female either.