On a side note, this lich is freakin' stupid. Like, intelligence 8 post-template. Sorcerers these days…
When you decide to exist indefinitely, respawning no matter what and having nothing to fear from any kind of opposition that isn't either extremely high-level or optimised, with a single caveat of all of it going away if you fail to keep a single little item intact, you do not, i repeat, YOU DO NOT bet on assumptions like "every being that ever arises in this world or the next will be aware of the bomb's destructive potential and absolutely unwilling to risk it". I'm not talking about all the ways to avoid countryside blowing up which were discussed in this thread; i'm talking about the fact that world is rife with madmen, deities, evil races and evil individuals, kenders, elves, trolls, fanatics willing to crush some eggs in order to get rid of you, avengers who won't care how many beings you hold hostage, people with pool impulse control, people with poor memory and/or poor attention to whom the connection between "boom" and "big red button" won't occur until they press it… The list goes on and on, and assuming none of those will ever happen to be amongst your enemies is highly dumb.
And you do not, under any circumstances, decide that "item that provides me with eternal immortality and near-inkillability for as long as it is not destroyed" and "item that self-destructs during proper execution of its main designated function, which is easy to trigger, easily recognisable and widely known" combine well. You know, i retract my statement about intelligence 8; int 4 post-template sounds a bit more like it.
All that being said, leading the world to mistakenly believe the bomb is your phylactery can lead to a good laugh.