Don't worry. Opening a file every 10 seconds is to a CPU like a fly is to a windshield: hardly noticable

Here a short test:

time perl -e 'for (1..100000) { open($f,"<","./t7.pl"); close($f); }'

real    0m0.446s
user    0m0.229s
sys     0m0.201s
[download]

So my machine can open and close a file about 250000 times a seconds