In the last two years I have:
burned charcoal bricks with incense from Mount Athos and the United States.
burned charcoal powder with incense from Mount Athos and the United States
burned half bricks with incense from Mount Athos and the United States.
burned nickel sized bricks with incense from Mount Athos and the United States.
burned orthodox 'cones' hand made by the folks at Desert Father's Incense.
burned orthodox 'sticks' hand made by the folks at Desert Father's Incense.
I use either orthodoxincense.com or deseretfathersincense.com
both are small operations and orthodoxincense supports Fr. Deacon Seraphim's family.
The two years of constant trial came from being in a mixed marriage - orthodox and atheist. I was constantly in search of something I could burn where we would be at peace.
I found that Frankincense is out - and though I absolutely love it, it is becoming endangered, so not a bad thing.
Right now, depending on where and what, I burn either the cones or I use the nickle sized charcoal and place a few incense 'seeds' near by so that I can continue to feed the coal as I pray. I've noticed it lasts right at 45 minutes most of the time.
The cones are becoming less and less frequent - as the need for them becomes less. There is just something about monastic made incense.
I found that the powder was a little difficult to manage - and would get everywhere if I wasn't very very careful, but it does burn nice - but not for 45 minutes.
The larger charcoals simply didn't burn all the way, though I have a different brand that I'm going to try, maybe they will do better.
Hope this helps.