I see investing as a long-term activity. If I can buy shares in great companies for my ISA, I think it makes sense to hold them for years and hopefully see business success mirrored in share performance.

With that long-term approach to investing in mind, here is a trio of shares I would be happy to own in my ISA for years to come.

Unilever

Years and decades from now, billions of people will still be shampooing their hair and washing their clothes regularly.

That ongoing demand explains the appeal of the consumer goods industry. But lots of companies operate in that space – so I am looking for ones I think have a competitive advantage. That is where Unilever (LSE: ULVR) looms into view for my ISA.

The owner of brands such as Dove and Marmite is able to charge a premium price for its products thanks to unique branding and proprietary formulations.

Billions of people use Unilever products each day, making it a profit machine. Last year, the London-based firm earned around £6bn in profits after tax.

A weak economy in some markets could see lower sales of pricy products, hurting sales. Unilever’s price-to-earnings ratio of 19 is higher than I would like (and higher than it was a few months ago) but if I had spare cash in my ISA, I’d be happy to spend some on the soapmaker’s shares.

Phoenix Group

Another share I would be happy to add to my ISA if I had spare cash to invest is FTSE 100 financial services giant Phoenix (LSE: PHNX).

The firm’s collection of pension and retirement companies is a significant generator of cash. That has helped Phoenix raise its dividend annually in recent years.

Last year saw dividend growth of around 3.6%. That means that Phoenix now offers a dividend yield of 10.6%, putting it in the very top tier of FTSE 100 shares by yield.

Dividends are never guaranteed, of course, and like all firms, Phoenix faces risks. For example, it carries an extensive book of mortgages. If a property market correction leads to bigger losses than expected on that mortgage book, profits could tumble.

But from a long-term perspective, I think this proven income share would be a good fit for my ISA.

British American Tobacco

Another share I would happily hold for years in my ISA is one I already own and have no plans to sell: British American Tobacco (LSE: BATS).

At surface level, the risk here may seem very high despite the attraction of a 9.7% yield. After all, cigarette use is declining in most markets. As the company noted last week, industry-wide cigarette volumes in the key US market are 9% lower so far this year than they were in the same period last year.

But the company has proven it can weather storms before. It is investing heavily to grow its non-cigarette business. It has been selling down shares in an Indian company and buying back its own shares, making it cheaper to sustain its juicy dividend.

It maintained its outlook for this year and expects to keep growing revenues in coming years. I plan to keep holding this lucrative income share.