You would be required to file prior forms only if the IRS audits your return and makes an issue of it.
Are you serious? You "only" need to file a required form if audited? How about the tax law that requires it? Is it OK to under report income until you are caught? I can't believe you actually said that.
Unfortunately, as tax court cases show, the IRS often does investigate that proper 8606 forms were filed when nondeductible contribution basis is claimed and then they deny the claim if the forms are missing. The IRS probably does not look if 8606 forms were filed, year-to-year, but when distributions are taken and a basis is claimed then can, and do, verify the basis against filed 8606 forms.
Best to do it right to start with and not open a can of worms later.