Extended-Stay Trips Gain Popularity : Variety of packages enable vacationers to save money while enduring a minimum of hassles.

Extended-stay vacations have become very popular with seniors, and for good reason.

Travelers avoid the sometimes-daily hassles of packing and unpacking forced by shuffling from one hotel to another, and save money by utilizing kitchen facilities rather than eating out every meal.

At least six tour companies now offer such vacation packages specifically for seniors, mostly to foreign destinations. Typically, the extended stays are in an apartment or hotel and last anywhere from a week to a month. The tours all include round-trip air transportation, transfers, a varying amount of sightseeing, other activities and entertainment.

Here’s a rundown on the major tour operators and their extended-stay offerings that cater to seniors:

* Grand Circle Travel: The Boston-based senior tour specialist is, along with the AARP Travel Experience From American Express, one of the established leaders in the field. Grand Circle offers extended stays (two weeks or more) in London, Paris, Switzerland, Italy and Ireland. It uses either apartments or hotels and includes many meals, and has its own program director on hand at each location. A wide range of social and cultural activities are included in the price, along with a selection of optional sightseeing tours (at additional cost).

A two-week extended stay in the spring to Gstaad, Switzerland, with first-class hotel, 28 meals, transfers and activities, costs $2,345 per person, double occupancy, including round trip from Los Angeles. Tax and security charges are not included. For more information: Grand Circle Travel, 347 Congress St., Boston, Mass. 02210, (800) 221-2610. Not sold through travel agents.

* AARP Travel Experience From American Express: A program called At Home features vacation stays of one or more weeks in theCosta del Sol or Mallorca, Spain; the Algarve or Estoril, Portugal; Istanbul or Antalya, Turkey; London; Pompano Beach, Fla., or even Palm Springs. Accommodations are mostly in apartments with kitchens, including a welcoming bag of groceries, or in hotels with breakfast included. A host is on hand at the destinations. There are optional local sightseeing tours.

A two-week extended stay in Torremolinos, Spain, this spring includes a one-bedroom apartment, full kitchen, continental breakfast daily, supermarket, restaurant and three pools on site, plus a wide range of activities for $1,189 per person, double, including round trip from New York. Taxes and security charges are not included. AARP Travel Experience, P.O. Box 7625, Norcross, Ga. 30091-7625, (800) 927-0111.

* Saga Holidays: Another major player in the mature market, its extensive tour-filled 1993 Travel Planner includes three extended stay-type vacations--Bermuda; Costa Rica and Guatemala, and Palm Springs.

Weeklong stays in Bermuda include a choice of two hotels, one with unlimited golf on its 18-hole course, plus breakfast daily, an option to buy a $99 dine-around plan for seven dinners at selected island restaurants, and a good selection of activities. A week this spring at the Belmont Hotel Golf and Country Club costs $1,349 per person, double, including round trip from Los Angeles.

The combination Costa Rica/ Guatemala visit is not billed as an extended-stay vacation but comes close, what with a week in each capital city, breakfast daily, a local host on hand, varied day and evening social programs, and a half-day sightseeing in each city, plus longer optional tours. Saga Holidays, 222 Berkeley St., Boston, Mass. 02116, (800) 343-0273. Not sold through travel agents.

* Sun Holidays: This company specializes in extended stays solely in Spain and Portugal. It offers a wide choice of either apartments or hotels along Portugal’s Algarve, Cascais and the island of Madeira, and Spain’s Costa del Sol and Canary Islands. Sun has its own hosts on hand and has an innovative free local tour program. Properties also offer their own day and evening social programs. Hotel stays usually include breakfast, most often buffet-style.

Two spring weeks at an oceanfront four-star apartment on the Algarve, including a full kitchen, a pool and a garden restaurant, cost $1,029 per person, double, including round trip from New York. Sun Holidays, 26 Sixth St., Suite 603, Stamford, Conn. 06905, (800) 243-2057.

* Diana Presents: The firm’s “60 Plus” tours, designed strictly for seniors, focus on Italy’s Amalfi Coast in stays of 15, 22 or 29 days. They feature three-star hotels, three meals daily, a local tour host and a good program of local activities such as wine and food tasting, lectures and sightseeing excursions to places like Pompeii and Naples. A 15-day program this spring costs $3,199, including round-trip air from Los Angeles. Diana Presents, 301 Alden Ave., New Haven, Conn. 06515, (800) 441-3485.