Departing Heathrow

Hi!  I'm departing Terminal 3 Heathrow mid-afternoon Wednesday, to return to the US.  What can I expect? Anyone have an idea how long check-in and security lines have been midweek theses days, and how far in advance I should plan to get there?  Also, will I go through any kind of exit interview at immigration? Besides telling them that i am going home, what would they need to know? If I arrive early enough and get through the lines, are there any food or coffee options near the gates?  Thanks.

I flew mid-week in April, and it was pretty empty. Hardly a line at check-in or security.  No exit interview, either.  I was so early, it was a bit maddening. 

And yes, most of the food/shopping stuff is past security.  I'd call it a mini-mall, to be honest. 

United makes you show your boarding pass to get through to the gate, so get your coffee after security, but before you get to your gate!

I always arrive at least three hours ahead of time for any international flight.  The time goes by quickly and you've got peace of mind and less stress for it.  Once I was so early (flying out of Shannon,not Heathrow that time) that they bumped me up to an earlier flight and put me in *first class* as well!    I don't expect that to ever happen again, though.

I am sure to be there 2 hours early and always end up with tons of time, but wouldnt want to cut it short, just in case of any delays.  I think it depends more on time of day than day of week.  I generally leave Heathrow in the afternoon and have never had a measurable wait at security.  No exit interview is needed... you will not come in contact with any immigration officers until you re-enter the US and they will ask you where you were and sometimes why, but nothing more than that. 
There are a lot of coffee/food/newspaper options after security in Terminal 3.

Have a good flight.

I fly out of Terminal 3 when I go back to visit in the States. The last time I flew was last August and it was a ZOO!! Lots of people but the lines actually moved fairly quickly. I was travelling with my husband and 2 of my kids so it probably took me 5 times as long to do everything! We got to the airport 2 hours before departure and just had enough time to get baby food at Boots (which was busy as anything!) after checking in and then had to haul the baby seats on a 25 minute walk to our gate. I said all that to say, if we can do it in that amount of time then it should be a breeze for you!

I flew out last month from Terminal 3.  It took me roughly about half an hour to get through security.  This involves the usual x-ray of your carry-on, and a walk through passport control, (only ever glance at my passport, if there is even anyone there) and then you have to pass your footwear through x-ray after that.  However, when I have traveled at peak periods, (which I think now might qualify since it is summer) it has sometimes taken me almost an hour to get through security.

I think the longest time can be just checking in at the airline.  I always travel American (airmiles!) so I can only speak to that experience, and I don't know what the other airlines are doing.  They have recently opened up a DIY check-in and that has cut down the waiting time considerably.  That line used to be hideously long.

American has a new gate area that it is flying out of, and it takes a good 10-15 minutes to get there from the waiting area.  As others have mentioned, there are plenty of places to get a cup of coffee or other beverage once you get past security.  There is a huge duty free department, as well as high street shops like Boots, WH Smith, HMV, Curry's and high-end retailers like Harrod's and Burberry, so if you get there early, and sail right through security, you needn't be bored just sitting there!