Disclaimer: I manual fight. YMMV.
The desire that surrounds the supply of pet food is one of the manufactured anxieties in Elvenar. After awhile, it seems, it does not make a difference, really.
Case in point: very late in the last few Tournies, on a Saturday night, I was afflicted with a bout of boredom and decided to fight a few more encounters at the end of the time. Because of the limited time left it was not worth it to feed the firebird or the twilight bird. If the encounters became unwinnable I would just quit. I was in the high 30s provinces. Buff buildings had not expired, yet.
It was actually surprisingly easy to move into the 40s provinces and to progress quite a way. There were a few fights that I quit early on and regrouped with a different selection of troops - this cannot be done with auto-fight - and won my way through them. No negotiating.
At the end of all this I had a noticeable decrease in my troop level but by the next Tourney I was back in the normal range after using a few time boosts for training (I have hundreds of them). The tradeoff is a slight increase in training between Tournies. Occasionally, one 12 hour use of Pet Food with the Brown Bear is worth 2 24 hour feeds of the firebird, with or without the twilight bird.
Now, there are developing cities that do not have an abundance of Supplies, workshops, Prosperity Tower, boosts and there are gamers who seek to be in the top ten score board for their server and there are rivalries (inter-FS, intra-FS, overt and unexpressed) that can consume gamers. These are the situations that give rise to pet food lust. But for one who just 'goes with the flow' of Elvenar bits and bytes there is no issue.
Pet Food is used for other things, operating in situations regarding MA and FA, but I am not addressing these because they also are not important to me.
Game lust=Pet Food anxiety.
Earlier in this thread I said that Twilight was good because it gave back without using boosts. But boosts become a glut in inventory so easily if used efficiently and not willy-nilly for every upgrade interval. Therefore the 50% benefit given by Brown Bear outscores the 5% benefit given by Twilight for the same time interval because the boosts are so abundant and cheap (don't tell the Devs this!).