It would seem that exceeding 30 contiguous days would cause a break in your "uninterrupted period of residence" in the foreign country. However return trips, each of which is less than 30 days, might not cause a break Note the word "trips" (plural) in the citation below. Consulting your tax professional would be wise to confirm your situation..
See the IRS bona fide residence qualification criteria (with examples) and the citation below at:
https://www.irs.gov/individuals/international-taxpayers/foreign-earned-income-exclusion-bona-fide-re...
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Uninterrupted Period Including Entire Tax Year
To qualify for bona fide residence, you must reside in a foreign country for an uninterrupted period that includes an entire tax year. An entire tax year is from January 1 through December 31 for taxpayers who file their income tax returns on a calendar year basis. During the period of bona fide residence in a foreign country, you can leave the country for brief or temporary trips back to the United States or elsewhere for vacation or business.
To keep your status as a bona fide resident of a foreign country, you must have a clear intention of returning from such trips, without unreasonable delay, to your foreign residence or to a new bona fide residence in another foreign country."
