Is there a hint of danger in the air? BUFF!
Did the GM start narrating a scene? Must be danger ahead – Interrupt to BUFF BEFORE INITIATIVE!
Is it getting close to the end of the day? BUFF NOW just in case!
Is this likely the last fight before the party has to rest? BUFF A, BUFF B, BUFF C, AND BUFF D.
Did an encounter start before buffing? Sub-question – can I reasonably argue that my character would have already buffed? Not buying it? Lame… BUFF!
In all seriousness, this gets old. It’s terrible for the fighters at the table, and it probably gets old even if you ARE a spell caster. Don’t you just wish your buff spells lasted all day and you didn’t worry about all that? Why can’t they? Just have a few less spells, or make the buffs a little less powerful. Resource management was built in when you decided to add that buff spell to your repertoire for the day instead of a different spell. I’ll let one-shot mundane or one-shot magic items act as the “special” buff for boss-level combats.