Internet speeds home Wi-Fi

Sounds great, but just stated my MiFi box done really well where I live 20-30 MB download and 5 upload on occasion. That's why I went to the home internet thinking it would be better the same at first. Then a little better but approximately 25-35 down and 10 Up I was happy with that. Then I have had issues past year at least. Constantly getting support to help get it back to working. Even said I need a new home internet box. Work well for a bit then back to the same issue. You would think if it worked well for few months or so it should be fine with the same speed constantly. I am not sure what goes on during the time frame of working decent for me, to just crapping out constantly again. It doesn't make sense to work well for a few months then not.