It takes a long time to send a message with my GPSMAP67i

This is way longer than it should be. It is possible that the unit is defective.

The other possibility is that you don't have fix, but that's even less likely than failure to contact the Iridium network. (The unit resists sending a message without a location.) Besides, I think it eventually will prompt to send without a fix - and in a lot less than 20 minutes.

You can try a full reset. this loses all user data on the unit, so sync first. This will also require you to repeat the outdoor portion of activation. This is the "conventional wisdom" when something goes wrong. It may not help, but it's the first thing that tech support will suggest.

If that does not help, open a support ticket.

I did not mention the carry position because it appears that you have it right. Pants pocket, shirt pocket, in the pack -- all bad ideas. Your body and/or the pack block too much of the sky.

Mine shows "checking in" continuously but it actually almost sends the check in instantly. It may be a bug in the interface. I have tested this several times by sending the check in to myself

interesting.  I see the times of the emails( when I send the checkin updates), and they are close to times when I sent,  .. but I don't know if it keeps the sent time, even while it is trying to send.  In last 2 instances , it took 30 minutes before "checking in" was clear from the inreach... I actually think that having that checking , continuously going is also draining the battery too, as it keeps "trying" to send. .... my old explorer+ I could hike 20 miles and it might use up 10% .. now I'll hike 10 miles and it uses up 20% of the battery .. which is supposed to last longer . I dont get it. 

Someone from garmin might chime in here. That "Checking in" might also be waiting to hear back a confirmation of sent. In that case probably doesn't use much extra battery. The device is always is listening for new messages....I have not noticed any extra battery drain that was alarming...

This is not entirely correct. "Sending a message" (no matter what kind) or a track point ALWAYS includes waiting for the iR satellite network to acknowledge receipt of the message. This does NOT mean that it has made it even as far as the Garmin servers, let alone to the email or SMS recipient. It just means that the device has successfully handed off to the Iridium network - which is all the device can do.

If you send without a clear sky view, the device will "retry" until it gets an acknowledgement. If this takes a long time, it WILL suck battery regardless of the device.

The simplest and most reliable thing is to look for the "curved up-arrow" icon in the status line at the top of the screen. That indicates that the device's iR modem is "on". Which means using battery. While retrying, it won't necessarily be on continuously - but you will see it for long intervals and frequently.

The device is NOT always listening for new messages. It automatically checks for messages once an hour. And it checks when you manually request a check. It also checks as a side-effect of successfully sending a message or a track point. The automatic once an hour check is ALSO a possible culprit in battery drain. If the device is powered up but has no clear sky view, it will (re)try VERY hard to complete the message check once it starts. Which sucks battery because the iR modem is on.

IMO, it is still possible that the OP's device is defective.

As I mentioned, I have tested it several times in different circumstances. Every time it does send the check in and I receive it in my email quickly, within seconds. But the interface still says "Checking in" for a long time. I think it is the confirmation and any other sync data that is taking longer to arrive.

"The device is NOT always listening for new messages." Of course, it does only listen with some frequency. To say the least it would overwhelm the back end server if it constantly was receiving push messages.....

The check as a side-effect of sending is "free" unless there IS a waiting message. There is a flag in the acknowledgement for the send that says "message is waiting for this device". When it sees that, the device initiates a mail check.

There is also an extended check (frequent checks for 10 minutes or so) after the device sends a message. The intent here is to catch an immediate (more or less) reply from the recipient - so you can carry on a "conversation".  Without this, you would not see the "immediate" reply for an hour (in the absence of other traffic from the device).

Point is that it is hard to predict battery drain unless you scrupulously maintain a clear view of the sky.