Do any suppliers give a discount if purchasing several tubes of gastroguard? Or are there any coupons? I need to use a tube a day for 8 weeks. Thanks.

I would think a tube per day for one month should be plenty, but whatever your vet recommends. 

you can do an online rebate if you keep your original invoice .

go to https://www.boehringeringelheimequinerebates.com/#/home

I've attached a picture of the rebate options

95E964EF-9707-4F43-A532-8433F6351F58.jpeg (86KB - 249 downloads)

Don't know if it helps but the GastroGard and the UlcerGard are the same thing. You can give 1 tube of UlcerGard daily for treatment with the same effectiveness. And a lot of times it's a little cheaper 

Very true. 
some people are so using Rakuten in addition to their rebate.

the Ulcergard rebate is listed on the same site that I put the link to as the Gastrogard. (Previous link wasn't working so I corrected it)