Hi;
Assemble Abomination has skill called “Age of Undeath”. You can now only consume minions from the Summon Skeletons and Summon Skeletal Mages and Abomination does not start to decay until you control 6 or more such minions at the same time.
But Abomination, skeleton and golem health decay regardless of how many minions there are when abomination is summoned.