How do you “lay up treasure in heaven?” This sounds like the classic bad joke where the baptist minister throws the offering in the air and gives the Lord everything that lands outside of a designated circle, the priest throws the offering in the air and gives the Lord everything that lands inside the designated circle, and the Rabbi throws the offering in the air and gives the Lord everything that He can catch.
The command to lay up treasure in heaven seems to be contrasted with the command to not lay up treasure on earth. Laying up treasure on earth seems to suggest investing time, attention, emotion or concern in the “stuff” of the world. Laying up treasure in heaven, then, would be willingly sacrificing time, attention, emotion or concern to the Lord's kingdom.
By default, we are all storing up treasure in heaven the same way we take the extra coins that we don't use at the end of the day and throw them in a jar. Whatever time or interest we are not otherwise using for our pleasure we toss to God. This seems like a pretty lousy “retirement” plan.