I would suggest you to accept a full BGP feed from your providers since one day or another you might need to access a route which is a /24 prefix and announced by only one of your neighbours.
If you just need to insure you have a full visibility of the 400k routes of the Internet here is a personal receipe I would try to reduce your router convergence time.
Let's say you have 2 BGP neighbours AS1 and AS2.
For the 2 feeds, define a prefix-list so as to reject any route that will contain the other BGP neighbour AS.
In front of AS1, reject every AS path that will contain AS2.
In front of AS2, reject every AS path that will contain AS1.
Hence an AS path which is provided by your 2 neighbours will never lead to a
A route accessible through only one of your neighbours will never be eliminated.
The risk is that a route like: AS1 - AS2 - AS3, which is a shorter route than the one: AS2 - AS3, will be rejected. But this "coming from behind" route being the best is a rare practical case.