Well I thought your post came across as if you were advertising for a company I recorded the heart beat on my phone when the midwife first used the doppler, so I understand the excitement.
BUT it is a method of ultrasound, and it is generally accepted that ultrasound should be used with as little frequency as possible. A doppler applies more direct ultrasound waves on a more intense level - and extensive exposure has been linked to damaged / limited cell growth.
And on the other side to my previous point - they can make you panic if you can't pick them up. Presuming you're not medically trained, you will be just using it as the instruction booklet says. Well, say you heart the heartbeat at X o'clock, and a few hours later, your DH wants to listen, and you can't pick it up at Y o'clock. Baby has probably moved, and is in an awkward position, but it will just worry you. The number of visits to hospital my midwife said she had been present at where hysterical parents-to-be had come rushing up, still trying to use the doppler, screaming that they must be seen immediately because they knew something was wrong... In every case baby was fine, but that is why they are generally not advised by medical practitioners for home use, especially not daily.
If your DH likes listening - DP found he could hear / feel DS if he put his ear to my belly when I was laying down. He felt his first kick by doing this at maybe 17 weeks? Maybe try that. I still remember the look on DPs face when he looked up at me, shocked and said, "Was that a kick? I felt that! Was it a kick?".