I'm not sure it's actually true that you're losing as much as you think - people often believe they've forgotten way more than what actually happened. Once you've built a solid foundation, it doesn't disappear that easily, even if maybe your fluency dips a bit. The real trick is keeping it "active" without spending a fortune, and there are pretty simple ways to do it.
The most effective thing is consuming content in English that you actually enjoy: films, TV series, podcasts, books, whatever you prefer. That way it's not a chore, it's just entertainment. If you listen to podcasts while driving or working out, read news in English during your lunch break, watch a series in the evening - that's hours of natural exposure that costs nothing. If you want to push a bit harder, you could join online communities (forums, Reddit, Discord) where users talk about stuff you're interested in and write comments here and there. It doesn't have to be perfect; as you read and write, your brain naturally reactivates everything.
If you feel like vocabulary is what's holding you back the most, free apps like Duolingo or Anki can help with a few minutes a day, but honestly passive content consumption works better for people who already have a foundation. Maybe every once in a while you find free language exchanges where you can talk to native speakers learning Italian - it's a swap, nobody pays anything. Consistency matters more than quantity: 20 minutes every day is better than one long lesson once a month.