I try to get mine as close to the vessel as possible. When fermenting, I sandwich it between a small piece of bubble wrap and the ale pail with a piece of tape. The bubble wrap insulates it from the ambient air, forcing it to pick up on the temp of the ale pail (and fermenting beer insdie). This gives it a better ability to control the fermentation temperature which is what you care about anyway (active fermentation creates heat you want to dissipate). For bottle aging, I do the same thing, just with a bottle of the beer.