^I just want to share my thoughts about the other side of the coin.
Personally i have gone to 2, maybe 3 bridal fairs after I got engaged without booking anything. I just collected brochures for me to know about the prices and suppliers available.
My rule is never to get pressured to book a supplier that I haven't even researched yet, just because they offer a huge discount at the bridal fair. Of course they will, they will do just about ANYTHING to get bookings there because they paid so much to participate, lol. But if I backread after and find out that they're totally not worth it, then I'd end up regretting booking them at all. So just to be safe and avoid changing suppliers (which is of course magastos din in the end), I go home with just flyers.

In the first 3 months, we booked almost all our major suppliers (Venue, Photo, Video, Gown, HMUA, Coordinator) without discounts and outside of a bridal fair, partly because they dont join fairs much and also so we can wait until we're "sure" about choosing each of them before actually booking.
When the January fairs came along, it was just good timing because we were about to book our L&S and LED wall suppliers naman na talaga this month. We got small discounts, and they were the first ones I ever booked from a fair.
But honestly, if they are not your top (and only) choice for each category and you just felt compelled to get the discount they offer at the fair, DON'T book them! You may regret it.

I've read some brides here saying they changed 2 or 3 of their suppliers because after booking sa bridal fair they were scared they wouldn't perform pala after doing research (and may negative reviews)... that's more magastos diba, you could have used the forfeited dp to get a better quality supplier. It makes me cringe to read posts na "we booked xxxxx during the fair kasi maganda package malaki discount, sino dito kumuha sa kanila, ok ba sila?" Sana may research naman kahit papano before shelling out money. Budget bride or not, it's more of being practical.

I'm proud to say that in the 15 suppliers we've chosen so far, kahit isa we have no doubts, and no plans of changing and we have full trust in them. So i feel like fully doing your homework is more important that securing discounts, if it comes down to choosing between.

Hope this helps!