skipped stitches sewing machine

Is it worth paying for repairs to an old sewing machine or just buy a new one?
I have a 30 year old Elna that I've had for the past 15 years (I bought it used). It recently stopped working. I plugged it in and it just stopped running. I also have a 30 year old Singer. My family gave it to me a couple years ago when my grandma passed away. No one else in the family wanted it. When my Elna died, I started using the Singer. The problem with the Singer is that it skips stitches when it zigzags and it won't wind bobbins. Is it worth trying to fix either of these machines? Should I just buy a new one? Do they make sewing machines these days that will last 30 years?
Wow... I wasn't expecting this many good answers! Thank you all for answering.
No, today's machines will probably not last 30 years. But they do have more features.
Your best bet, is to take the Elna and the Singer to a local sewing Machine Repair shop.
Get an estimate on each, BEFORE you decide.
While you are waiting for the estimates, browse their used and new machines. Now you have an idea as to current sales prices.
Jot down any interesting machine names, numbers, features and prices.
NOW, With you repair estimates in hand, compare that to the new/used prices.
Now look at them in a firm, no nonsense way, and ask for their opinion.
If they recommend going "new/used", then ask what trade in allowance (they can use them for parts) you would get on your old machines.
If they recommend repairs, you have to decide whether you will fix both machines, or just one. If just one, ask which one they think is more worth fixing. Decide, and ask, if they will take the machine you are not getting fixed, as a trade in.
Don't fall for a hi-pressure talk. You can take all the info home and sleep on it.
If you are very good at sewing, ask if they might need a sewing tutor for new sewers. Might make a nice PT job. At any rate, if you are a good sewer, make up some quick business cards on your home PC. (Any good supply store carries cheap blanks, they are all "pre-cut", and just knock out of a page. Most current word processors have at least 1 template.) Be sure to leave a few card on their bulletin board.
This will minimize your costs, and maximixe your opportunities.
Hand Quilting 5 -- Stitching