The reason for the boundary is not arbitrary. Working exclusively with first year businesses means seeing the same problems repeatedly across many businesses, which is what turns individual experience into pattern recognition. That expertise is genuinely useful at the stage it addresses and it is not the expertise a business in year three needs, which is about scaling systems, managing people, and operating at a volume that changes what works.
A business three years in has different problems. The website that was correct for a solo operator may not suit a team. The processes that worked when you did everything need to work when others do. The marketing that reached your first customers may not reach the next hundred. Those are legitimate problems and they belong to somebody who works on them constantly.
That said, a specific question is a different thing from an engagement. If something comes up that sits squarely in what I know, ask rather than assuming the door is closed. Frequently the answer takes ten minutes and costs nothing, which is a better outcome for you than finding somebody new for a small question.
Defined project work is also worth raising. If there is a discrete piece of work with a clear boundary that matches what I do, the fact that the business is older does not automatically make it a poor fit. The exclusion is about ongoing arrangements at a stage where a different specialism serves you better, not about a specific task.
Expect an honest answer about fit rather than an attempt to take the work. Being told that somebody else would serve you better is the useful version of this conversation, and knowing who does good work at your current stage is part of being useful. An introduction costs nothing and is remembered.
Keep the documentation from the original engagement, since that is what makes any future conversation efficient. Decisions written down, accounts in your name, and a record of what was built means anybody picking it up starts from a position rather than from an investigation.
Consider whether the recurring need indicates something structural, which is worth asking honestly. A business returning repeatedly for the same category of help may be missing capability internally rather than needing external work, and hiring or training is frequently the better answer than a series of engagements.
Then remember that the aim of the original work was for you not to need it. A business that comes back three years later with a genuinely new problem is a success. One that comes back because it never became self sufficient is a sign the first engagement missed something.
Keep the relationship rather than only the documentation, since a question answered quickly by somebody who already knows your situation is worth more than a new engagement with somebody who does not. A short message years later is welcome and costs nothing to send.
Ask early rather than after a problem has developed, since the questions that are cheap to answer are the ones raised before a decision is made. A conversation about whether something is a good idea takes minutes, and unpicking it afterward does not.
Expect your own situation to have changed more than you notice, since a business three years in frequently describes itself the way it did at the start. That gap is worth examining independently of whether you need external help.