Yes you can! As long as you keep the Silver status forever, banking points can go on forever.
I myself had originally wanted to bank around $3,000 in certificates and buy a new 60" HDTV (or whatever) for the $5 difference. The economy had other plans for me and when my last DVD player stopped working and that was followed 3 months later by my 26" TV; I printed off $300 in certs, went in and bought a new 32" TV and DVD player. With a $10 gift card I got from an earlier purchase, I ended up paying 54 cents out of pocket.
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Before posting I try to research everything first or use my own experiences. I do not now nor have I ever worked for Best Buy. I work for the competition.
If you respond to a post of mine, I will read it. I may or may not post in the thread again, but rest assured I will read your response