Every Day

Some people like to take specific live cultures strains at certain times, for example during pregnancy, or during the winter flu season. However, most people prefer to take a daily live cultures supplement on an ongoing basis to complement their gut bacteria. Research (1,2) to date suggests that long-term use is fine, as the body does not become dependent on the good bacteria.

Reference
(1). Mimura, T. et al. (2004). 'Once daily high dose probiotic therapy (VSL#3) for maintaining remission in recurrent or refractory pouchitis'. Gut, 53(1): 108-114. (2). Jacobsen et al., (1999). 'Screening of probiotic activities of 47 strains of Lactobacillus spp. by in vitro techniques and evaluation of the colonisation ability of 5 selected strains in humans'. Applied and Environmental Microbiology; 65 (11): 4949-4956
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If looking for alternatives to brands like Symprove, you should compare the cost, the recommended daily amount, and the quality of the strains. A high-quality supplement always lists the full strain names of the bacteria, not just the species, so you can check the supporting research. Optibac Every Day is a great alternative to Symprove and other similar brands; it out-performs most comparable products not only on price, but also on quality of the strains it contains.

The number of strains is not the most important thing to look for in a daily live cultures supplement. It is best to select a supplement containing highly researched friendly bacteria. Optibac Every Day contains the world-renowned Lactobacillus acidophilus/helveticus Rosell-52 and Lactobacillus rhamnosus Rosell-11®, proven to survive stomach acidity and reach the gut alive(1)

References
1. Nagulesapillai, V., Belvis, J., Tompkins, T. and Girard, S.-A. (2017), Detection and Quantification of Probiotic Strains in Clinical Fecal Samples of Healthy Adults by Real-time PCR. The FASEB Journal, 31: lb207-lb207. https://doi.org/10.1096/fasebj.31.1_supplement.lb207
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Yes, it is safe and generally advisable to take a daily friendly bacteria supplement. Good bacteria only colonise in the gut for a few weeks and research(1,2,3) suggests that taking regular digestive supplements helps to complement the gut microbiome.

References
1. Mimura, T. et al. (2004). 'Once daily high dose probiotic therapy (VSL#3) for maintaining remission in recurrent or refractory pouchitis'. Gut, 53(1): 108-114 2. Jacobsen et al., 1999. 'Screening of probiotic activities of 47 strains of Lactobacillus spp. by in vitro techniques and evaluation of the colonisation ability of 5 selected strains in humans'. Applied and Environmental Microbiology; 65 (11): 4949-4956 3. Nagulesapillai, V., Belvis, J., Tompkins, T. and Girard, S.-A. (2017), Detection and Quantification of Probiotic Strains in Clinical Fecal Samples of Healthy Adults by Real-time PCR. The FASEB Journal, 31: lb207-lb207. https://doi.org/10.1096/fasebj.31.1_supplement.lb207
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